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	$146.48	7.286%	$157.1525	$157.15	$157.15	$157.20
Purchase #2	$146.96	11.832%	$164.3483	$164.35	$164.35	$164.30
Purchase #3	$33.79	9.452%	$36.9838	$36.98	$37.00	$37.00
Purchase #4	$42.81	10.111%	$47.1385	$47.14	$47.15	$47.10
Purchase #5	$57.33	7.750%	$61.7731	$61.77	$61.75	$61.80
Purchase #6	$12.49	9.647%	$13.6949	$13.69	$13.70	$13.70
Purchase #7	$67.71	7.566%	$72.8329	$72.83	$72.85	$72.80
7 purchase totals =	$507.57		$553.9240	$553.91	$553.95	$553.90