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	$167.86	7.536%	$180.5099	$180.51	$180.50	$180.50
Purchase #2	$67.47	7.411%	$72.4702	$72.47	$72.45	$72.50
Purchase #3	$160.91	5.428%	$169.6442	$169.64	$169.65	$169.60
Purchase #4	$223.99	13.240%	$253.6463	$253.65	$253.65	$253.60
Purchase #5	$175.74	11.252%	$195.5143	$195.51	$195.50	$195.50
Purchase #6	$20.87	8.868%	$22.7208	$22.72	$22.70	$22.70
Purchase #7	$70.97	11.195%	$78.9151	$78.92	$78.90	$78.90
7 purchase totals =	$887.81		$973.4208	$973.42	$973.35	$973.30