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	$83.68	5.247%	$88.0707	$88.07	$88.05	$88.10
Purchase #2	$179.92	9.364%	$196.7677	$196.77	$196.75	$196.80
Purchase #3	$248.45	3.187%	$256.3681	$256.37	$256.35	$256.40
Purchase #4	$161.47	6.170%	$171.4327	$171.43	$171.45	$171.40
Purchase #5	$249.26	8.160%	$269.5996	$269.60	$269.60	$269.60
Purchase #6	$40.60	8.554%	$44.0729	$44.07	$44.05	$44.10
Purchase #7	$71.34	10.664%	$78.9477	$78.95	$78.95	$78.90
7 purchase totals =	$1,034.72		$1,105.2594	$1,105.26	$1,105.20	$1,105.30