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	$37.71	7.558%	$40.5601	$40.56	$40.55	$40.60
Purchase #2	$83.58	8.567%	$90.7403	$90.74	$90.75	$90.70
Purchase #3	$165.95	4.265%	$173.0278	$173.03	$173.05	$173.00
Purchase #4	$143.70	4.850%	$150.6695	$150.67	$150.65	$150.70
Purchase #5	$246.74	11.650%	$275.4852	$275.49	$275.50	$275.50
Purchase #6	$137.71	8.568%	$149.509	$149.51	$149.50	$149.50
Purchase #7	$193.61	12.295%	$217.4143	$217.41	$217.40	$217.40
7 purchase totals =	$1,009.00		$1,097.4062	$1,097.41	$1,097.40	$1,097.40