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	$193.89	11.664%	$216.5053	$216.51	$216.50	$216.50
Purchase #2	$37.37	9.252%	$40.8275	$40.83	$40.85	$40.80
Purchase #3	$143.62	6.374%	$152.7743	$152.77	$152.75	$152.80
Purchase #4	$205.93	5.324%	$216.8937	$216.89	$216.90	$216.90
Purchase #5	$143.39	4.538%	$149.897	$149.90	$149.90	$149.90
Purchase #6	$125.51	11.191%	$139.5558	$139.56	$139.55	$139.60
Purchase #7	$182.75	6.702%	$194.9979	$195.00	$195.00	$195.00
7 purchase totals =	$1,032.46		$1,111.4515	$1,111.46	$1,111.45	$1,111.50