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	$221.93	4.332%	$231.544	$231.54	$231.55	$231.50
Purchase #2	$179.48	13.598%	$203.8857	$203.89	$203.90	$203.90
Purchase #3	$126.75	11.538%	$141.3744	$141.37	$141.35	$141.40
Purchase #4	$138.57	9.353%	$151.5305	$151.53	$151.55	$151.50
Purchase #5	$245.67	6.388%	$261.3634	$261.36	$261.35	$261.40
Purchase #6	$245.50	13.474%	$278.5787	$278.58	$278.60	$278.60
Purchase #7	$126.65	7.446%	$136.0804	$136.08	$136.10	$136.10
7 purchase totals =	$1,284.55		$1,404.3571	$1,404.35	$1,404.40	$1,404.40