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	$222.37	5.527%	$234.6604	$234.66	$234.65	$234.70
Purchase #2	$204.79	10.167%	$225.611	$225.61	$225.60	$225.60
Purchase #3	$196.98	10.368%	$217.4029	$217.40	$217.40	$217.40
Purchase #4	$116.27	9.664%	$127.5063	$127.51	$127.50	$127.50
Purchase #5	$197.28	7.730%	$212.5297	$212.53	$212.55	$212.50
Purchase #6	$154.89	10.118%	$170.5618	$170.56	$170.55	$170.60
Purchase #7	$208.29	3.306%	$215.1761	$215.18	$215.20	$215.20
7 purchase totals =	$1,300.87		$1,403.4482	$1,403.45	$1,403.45	$1,403.50