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	$174.95	12.814%	$197.3681	$197.37	$197.35	$197.40
Purchase #2	$52.74	12.348%	$59.2523	$59.25	$59.25	$59.30
Purchase #3	$137.75	3.766%	$142.9377	$142.94	$142.95	$142.90
Purchase #4	$33.38	13.128%	$37.7621	$37.76	$37.75	$37.80
Purchase #5	$25.47	4.148%	$26.5265	$26.53	$26.55	$26.50
Purchase #6	$96.42	4.559%	$100.8158	$100.82	$100.80	$100.80
Purchase #7	$61.52	5.706%	$65.0303	$65.03	$65.05	$65.00
7 purchase totals =	$582.23		$629.6928	$629.70	$629.70	$629.70