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	$37.35	12.298%	$41.9433	$41.94	$41.95	$41.90
Purchase #2	$208.68	9.602%	$228.7175	$228.72	$228.70	$228.70
Purchase #3	$76.53	13.510%	$86.8692	$86.87	$86.85	$86.90
Purchase #4	$33.46	13.225%	$37.8851	$37.89	$37.90	$37.90
Purchase #5	$45.45	6.349%	$48.3356	$48.34	$48.35	$48.30
Purchase #6	$134.29	6.442%	$142.941	$142.94	$142.95	$142.90
Purchase #7	$130.69	11.838%	$146.1611	$146.16	$146.15	$146.20
7 purchase totals =	$666.45		$732.8528	$732.86	$732.85	$732.80