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	$78.95	13.302%	$89.4519	$89.45	$89.45	$89.50
Purchase #2	$198.26	13.166%	$224.3629	$224.36	$224.35	$224.40
Purchase #3	$174.51	11.575%	$194.7095	$194.71	$194.70	$194.70
Purchase #4	$228.37	8.501%	$247.7837	$247.78	$247.80	$247.80
Purchase #5	$59.86	8.341%	$64.8529	$64.85	$64.85	$64.90
Purchase #6	$20.69	5.115%	$21.7483	$21.75	$21.75	$21.70
Purchase #7	$242.61	3.600%	$251.344	$251.34	$251.35	$251.30
7 purchase totals =	$1,003.25		$1,094.2532	$1,094.24	$1,094.25	$1,094.30