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	$181.69	8.373%	$196.9029	$196.90	$196.90	$196.90
Purchase #2	$67.33	13.496%	$76.4169	$76.42	$76.40	$76.40
Purchase #3	$177.81	12.779%	$200.5323	$200.53	$200.55	$200.50
Purchase #4	$50.70	5.743%	$53.6117	$53.61	$53.60	$53.60
Purchase #5	$56.74	10.348%	$62.6115	$62.61	$62.60	$62.60
Purchase #6	$112.49	12.634%	$126.702	$126.70	$126.70	$126.70
Purchase #7	$132.75	12.680%	$149.5827	$149.58	$149.60	$149.60
7 purchase totals =	$779.51		$866.3600	$866.35	$866.35	$866.30