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	$171.74	10.283%	$189.4	$189.40	$189.40	$189.40
Purchase #2	$213.82	11.151%	$237.6631	$237.66	$237.65	$237.70
Purchase #3	$157.58	9.484%	$172.5249	$172.52	$172.50	$172.50
Purchase #4	$126.37	4.118%	$131.5739	$131.57	$131.55	$131.60
Purchase #5	$92.77	3.801%	$96.2962	$96.30	$96.30	$96.30
Purchase #6	$49.67	8.697%	$53.9898	$53.99	$54.00	$54.00
Purchase #7	$242.87	12.615%	$273.5081	$273.51	$273.50	$273.50
7 purchase totals =	$1,054.82		$1,154.9560	$1,154.95	$1,154.90	$1,155.00