Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$185.60	13.103%	$209.9192	$209.92	$209.90	$209.90
Purchase #2	$169.36	12.107%	$189.8644	$189.86	$189.85	$189.90
Purchase #3	$40.30	4.837%	$42.2493	$42.25	$42.25	$42.20
Purchase #4	$159.52	7.484%	$171.4585	$171.46	$171.45	$171.50
Purchase #5	$160.63	10.396%	$177.3291	$177.33	$177.35	$177.30
Purchase #6	$199.72	12.136%	$223.958	$223.96	$223.95	$224.00
Purchase #7	$174.58	3.142%	$180.0653	$180.07	$180.05	$180.10
7 purchase totals =	$1,089.71		$1,194.8438	$1,194.85	$1,194.80	$1,194.90