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	$225.37	7.309%	$241.8423	$241.84	$241.85	$241.80
Purchase #2	$227.89	12.578%	$256.554	$256.55	$256.55	$256.60
Purchase #3	$130.68	10.434%	$144.3152	$144.32	$144.30	$144.30
Purchase #4	$144.90	9.632%	$158.8568	$158.86	$158.85	$158.90
Purchase #5	$67.63	5.236%	$71.1711	$71.17	$71.15	$71.20
Purchase #6	$14.48	9.466%	$15.8507	$15.85	$15.85	$15.90
Purchase #7	$64.85	4.504%	$67.7708	$67.77	$67.75	$67.80
7 purchase totals =	$875.80		$956.3609	$956.36	$956.30	$956.50