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	$172.96	13.578%	$196.4445	$196.44	$196.45	$196.40
Purchase #2	$233.29	13.257%	$264.2173	$264.22	$264.20	$264.20
Purchase #3	$53.76	11.394%	$59.8854	$59.89	$59.90	$59.90
Purchase #4	$199.79	4.529%	$208.8385	$208.84	$208.85	$208.80
Purchase #5	$158.30	7.459%	$170.1076	$170.11	$170.10	$170.10
Purchase #6	$190.34	3.473%	$196.9505	$196.95	$196.95	$197.00
Purchase #7	$48.99	8.662%	$53.2335	$53.23	$53.25	$53.20
7 purchase totals =	$1,057.43		$1,149.6773	$1,149.68	$1,149.70	$1,149.60