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	$104.43	3.657%	$108.249	$108.25	$108.25	$108.20
Purchase #2	$80.44	3.869%	$83.5522	$83.55	$83.55	$83.60
Purchase #3	$239.70	6.182%	$254.5183	$254.52	$254.50	$254.50
Purchase #4	$33.63	10.645%	$37.2099	$37.21	$37.20	$37.20
Purchase #5	$21.53	6.386%	$22.9049	$22.90	$22.90	$22.90
Purchase #6	$125.72	4.463%	$131.3309	$131.33	$131.35	$131.30
Purchase #7	$90.76	11.199%	$100.9242	$100.92	$100.90	$100.90
7 purchase totals =	$696.21		$738.6894	$738.68	$738.65	$738.60