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	$235.80	12.251%	$264.6879	$264.69	$264.70	$264.70
Purchase #2	$24.54	3.455%	$25.3879	$25.39	$25.40	$25.40
Purchase #3	$210.64	6.733%	$224.8224	$224.82	$224.80	$224.80
Purchase #4	$223.40	3.648%	$231.5496	$231.55	$231.55	$231.50
Purchase #5	$26.80	5.570%	$28.2928	$28.29	$28.30	$28.30
Purchase #6	$234.27	9.158%	$255.7244	$255.72	$255.70	$255.70
Purchase #7	$79.47	5.146%	$83.5595	$83.56	$83.55	$83.60
7 purchase totals =	$1,034.92		$1,114.0245	$1,114.02	$1,114.00	$1,114.00