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	$38.71	3.695%	$40.1403	$40.14	$40.15	$40.10
Purchase #2	$22.77	3.311%	$23.5239	$23.52	$23.50	$23.50
Purchase #3	$75.68	3.309%	$78.1843	$78.18	$78.20	$78.20
Purchase #4	$138.70	4.171%	$144.4852	$144.49	$144.50	$144.50
Purchase #5	$140.33	10.860%	$155.5698	$155.57	$155.55	$155.60
Purchase #6	$34.39	9.785%	$37.7551	$37.76	$37.75	$37.80
Purchase #7	$22.58	13.760%	$25.687	$25.69	$25.70	$25.70
7 purchase totals =	$473.16		$505.3456	$505.35	$505.35	$505.40