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	$15.69	3.371%	$16.2189	$16.22	$16.20	$16.20
Purchase #2	$196.48	11.611%	$219.2933	$219.29	$219.30	$219.30
Purchase #3	$162.57	6.699%	$173.4606	$173.46	$173.45	$173.50
Purchase #4	$149.31	6.576%	$159.1286	$159.13	$159.15	$159.10
Purchase #5	$223.87	13.237%	$253.5037	$253.50	$253.50	$253.50
Purchase #6	$210.33	11.299%	$234.0952	$234.10	$234.10	$234.10
Purchase #7	$36.34	12.265%	$40.7971	$40.80	$40.80	$40.80
7 purchase totals =	$994.59		$1,096.4974	$1,096.50	$1,096.50	$1,096.50