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	$35.59	5.741%	$37.6332	$37.63	$37.65	$37.60
Purchase #2	$176.61	10.488%	$195.1329	$195.13	$195.15	$195.10
Purchase #3	$122.38	4.533%	$127.9275	$127.93	$127.95	$127.90
Purchase #4	$228.56	7.589%	$245.9054	$245.91	$245.90	$245.90
Purchase #5	$206.58	7.543%	$222.1623	$222.16	$222.15	$222.20
Purchase #6	$25.56	12.643%	$28.7916	$28.79	$28.80	$28.80
Purchase #7	$66.91	8.638%	$72.6897	$72.69	$72.70	$72.70
7 purchase totals =	$862.19		$930.2426	$930.24	$930.30	$930.20