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	$135.51	11.851%	$151.5693	$151.57	$151.55	$151.60
Purchase #2	$53.86	10.190%	$59.3483	$59.35	$59.35	$59.30
Purchase #3	$206.50	3.756%	$214.2561	$214.26	$214.25	$214.30
Purchase #4	$243.82	13.759%	$277.3672	$277.37	$277.35	$277.40
Purchase #5	$174.65	10.794%	$193.5017	$193.50	$193.50	$193.50
Purchase #6	$228.38	7.854%	$246.317	$246.32	$246.30	$246.30
Purchase #7	$100.75	10.411%	$111.2391	$111.24	$111.25	$111.20
7 purchase totals =	$1,143.47		$1,253.5987	$1,253.61	$1,253.55	$1,253.60