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	$92.88	8.354%	$100.6392	$100.64	$100.65	$100.60
Purchase #2	$16.76	9.398%	$18.3351	$18.34	$18.35	$18.30
Purchase #3	$50.88	6.212%	$54.0407	$54.04	$54.05	$54.00
Purchase #4	$30.61	9.311%	$33.4601	$33.46	$33.45	$33.50
Purchase #5	$50.26	9.649%	$55.1096	$55.11	$55.10	$55.10
Purchase #6	$111.41	6.182%	$118.2974	$118.30	$118.30	$118.30
Purchase #7	$111.80	11.862%	$125.0617	$125.06	$125.05	$125.10
7 purchase totals =	$464.60		$504.9438	$504.95	$504.95	$504.90