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	$79.81	6.638%	$85.1078	$85.11	$85.10	$85.10
Purchase #2	$30.43	10.110%	$33.5065	$33.51	$33.50	$33.50
Purchase #3	$35.83	4.861%	$37.5717	$37.57	$37.55	$37.60
Purchase #4	$199.35	9.166%	$217.6224	$217.62	$217.60	$217.60
Purchase #5	$225.60	8.197%	$244.0924	$244.09	$244.10	$244.10
Purchase #6	$177.82	10.548%	$196.5765	$196.58	$196.60	$196.60
Purchase #7	$139.28	12.521%	$156.7192	$156.72	$156.70	$156.70
7 purchase totals =	$888.12		$971.1965	$971.20	$971.15	$971.20