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	$97.45	13.105%	$110.2208	$110.22	$110.20	$110.20
Purchase #2	$189.70	10.579%	$209.7684	$209.77	$209.75	$209.80
Purchase #3	$173.89	4.228%	$181.2421	$181.24	$181.25	$181.20
Purchase #4	$10.27	6.235%	$10.9103	$10.91	$10.90	$10.90
Purchase #5	$152.42	8.605%	$165.5357	$165.54	$165.55	$165.50
Purchase #6	$38.52	4.414%	$40.2203	$40.22	$40.20	$40.20
Purchase #7	$33.55	10.664%	$37.1278	$37.13	$37.15	$37.10
7 purchase totals =	$695.80		$755.0254	$755.03	$755.00	$754.90