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	$41.89	11.194%	$46.5792	$46.58	$46.60	$46.60
Purchase #2	$18.53	12.774%	$20.897	$20.90	$20.90	$20.90
Purchase #3	$6.31	13.574%	$7.1665	$7.17	$7.15	$7.20
Purchase #4	$119.90	3.727%	$124.3687	$124.37	$124.35	$124.40
Purchase #5	$152.74	3.781%	$158.5151	$158.52	$158.50	$158.50
Purchase #6	$122.45	11.644%	$136.7081	$136.71	$136.70	$136.70
Purchase #7	$12.37	3.695%	$12.8271	$12.83	$12.85	$12.80
7 purchase totals =	$474.19		$507.0617	$507.08	$507.05	$507.10