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	$64.55	11.798%	$72.1656	$72.17	$72.15	$72.20
Purchase #2	$29.60	10.115%	$32.594	$32.59	$32.60	$32.60
Purchase #3	$97.70	4.802%	$102.3916	$102.39	$102.40	$102.40
Purchase #4	$40.39	13.525%	$45.8527	$45.85	$45.85	$45.90
Purchase #5	$10.72	13.819%	$12.2014	$12.20	$12.20	$12.20
Purchase #6	$221.26	3.770%	$229.6015	$229.60	$229.60	$229.60
Purchase #7	$50.73	9.758%	$55.6802	$55.68	$55.70	$55.70
7 purchase totals =	$514.95		$550.4870	$550.48	$550.50	$550.60