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	$165.96	3.727%	$172.1453	$172.15	$172.15	$172.10
Purchase #2	$136.39	11.413%	$151.9562	$151.96	$151.95	$152.00
Purchase #3	$5.44	13.749%	$6.1879	$6.19	$6.20	$6.20
Purchase #4	$27.90	5.741%	$29.5017	$29.50	$29.50	$29.50
Purchase #5	$67.31	4.562%	$70.3807	$70.38	$70.40	$70.40
Purchase #6	$124.90	4.105%	$130.0271	$130.03	$130.05	$130.00
Purchase #7	$36.49	3.868%	$37.9014	$37.90	$37.90	$37.90
7 purchase totals =	$564.39		$598.1003	$598.11	$598.15	$598.10