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	$245.34	7.580%	$263.9368	$263.94	$263.95	$263.90
Purchase #2	$36.75	3.173%	$37.9161	$37.92	$37.90	$37.90
Purchase #3	$48.62	12.239%	$54.5706	$54.57	$54.55	$54.60
Purchase #4	$66.95	6.652%	$71.4035	$71.40	$71.40	$71.40
Purchase #5	$130.51	5.697%	$137.9452	$137.95	$137.95	$137.90
Purchase #6	$73.84	4.826%	$77.4035	$77.40	$77.40	$77.40
Purchase #7	$72.52	8.281%	$78.5254	$78.53	$78.55	$78.50
7 purchase totals =	$674.53		$721.7011	$721.71	$721.70	$721.60