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	$143.83	3.490%	$148.8497	$148.85	$148.85	$148.80
Purchase #2	$193.98	3.472%	$200.715	$200.72	$200.70	$200.70
Purchase #3	$173.94	13.149%	$196.8114	$196.81	$196.80	$196.80
Purchase #4	$105.77	8.491%	$114.7509	$114.75	$114.75	$114.80
Purchase #5	$5.93	10.162%	$6.5326	$6.53	$6.55	$6.50
Purchase #6	$45.32	11.816%	$50.675	$50.68	$50.70	$50.70
Purchase #7	$98.74	6.651%	$105.3072	$105.31	$105.30	$105.30
7 purchase totals =	$767.51		$823.6418	$823.65	$823.65	$823.60