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	$142.52	3.462%	$147.454	$147.45	$147.45	$147.50
Purchase #2	$66.63	10.634%	$73.7154	$73.72	$73.70	$73.70
Purchase #3	$31.96	3.495%	$33.077	$33.08	$33.10	$33.10
Purchase #4	$229.30	11.447%	$255.548	$255.55	$255.55	$255.50
Purchase #5	$137.79	10.415%	$152.1408	$152.14	$152.15	$152.10
Purchase #6	$120.62	3.586%	$124.9454	$124.95	$124.95	$124.90
Purchase #7	$78.29	6.386%	$83.2896	$83.29	$83.30	$83.30
7 purchase totals =	$807.11		$870.1702	$870.18	$870.20	$870.10