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	$157.29	9.705%	$172.555	$172.56	$172.55	$172.60
Purchase #2	$56.91	4.380%	$59.4027	$59.40	$59.40	$59.40
Purchase #3	$104.79	5.398%	$110.4466	$110.45	$110.45	$110.40
Purchase #4	$194.52	5.831%	$205.8625	$205.86	$205.85	$205.90
Purchase #5	$127.96	12.624%	$144.1137	$144.11	$144.10	$144.10
Purchase #6	$145.87	12.373%	$163.9185	$163.92	$163.90	$163.90
Purchase #7	$207.54	5.257%	$218.4504	$218.45	$218.45	$218.50
7 purchase totals =	$994.88		$1,074.7494	$1,074.75	$1,074.70	$1,074.80