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	$173.28	9.748%	$190.1713	$190.17	$190.15	$190.20
Purchase #2	$152.60	6.630%	$162.7174	$162.72	$162.70	$162.70
Purchase #3	$59.81	12.433%	$67.2462	$67.25	$67.25	$67.20
Purchase #4	$229.50	5.726%	$242.6412	$242.64	$242.65	$242.60
Purchase #5	$22.55	10.199%	$24.8499	$24.85	$24.85	$24.80
Purchase #6	$156.83	10.803%	$173.7723	$173.77	$173.75	$173.80
Purchase #7	$150.98	5.574%	$159.3956	$159.40	$159.40	$159.40
7 purchase totals =	$945.55		$1,020.7939	$1,020.80	$1,020.75	$1,020.70