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	$64.25	9.735%	$70.5047	$70.50	$70.50	$70.50
Purchase #2	$32.26	13.819%	$36.718	$36.72	$36.70	$36.70
Purchase #3	$37.44	10.575%	$41.3993	$41.40	$41.40	$41.40
Purchase #4	$175.71	4.802%	$184.1476	$184.15	$184.15	$184.10
Purchase #5	$39.34	4.333%	$41.0446	$41.04	$41.05	$41.00
Purchase #6	$20.63	3.260%	$21.3025	$21.30	$21.30	$21.30
Purchase #7	$40.63	3.482%	$42.0447	$42.04	$42.05	$42.00
7 purchase totals =	$410.26		$437.1614	$437.15	$437.15	$437.00