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	$48.49	4.680%	$50.7593	$50.76	$50.75	$50.80
Purchase #2	$132.97	13.839%	$151.3717	$151.37	$151.35	$151.40
Purchase #3	$210.59	6.510%	$224.2994	$224.30	$224.30	$224.30
Purchase #4	$171.92	10.533%	$190.0283	$190.03	$190.05	$190.00
Purchase #5	$239.98	7.548%	$258.0937	$258.09	$258.10	$258.10
Purchase #6	$32.83	13.170%	$37.1537	$37.15	$37.15	$37.20
Purchase #7	$144.63	3.197%	$149.2538	$149.25	$149.25	$149.30
7 purchase totals =	$981.41		$1,060.9599	$1,060.95	$1,060.95	$1,061.10