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	$74.32	11.105%	$82.5732	$82.57	$82.55	$82.60
Purchase #2	$72.47	7.783%	$78.1103	$78.11	$78.10	$78.10
Purchase #3	$55.97	11.251%	$62.2672	$62.27	$62.25	$62.30
Purchase #4	$60.29	12.289%	$67.699	$67.70	$67.70	$67.70
Purchase #5	$72.74	7.477%	$78.1788	$78.18	$78.20	$78.20
Purchase #6	$205.72	4.717%	$215.4238	$215.42	$215.40	$215.40
Purchase #7	$158.65	4.553%	$165.8733	$165.87	$165.85	$165.90
7 purchase totals =	$700.16		$750.1256	$750.12	$750.05	$750.20