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	$33.75	11.186%	$37.5253	$37.53	$37.55	$37.50
Purchase #2	$74.59	9.453%	$81.641	$81.64	$81.65	$81.60
Purchase #3	$107.62	6.755%	$114.8897	$114.89	$114.90	$114.90
Purchase #4	$213.91	8.194%	$231.4378	$231.44	$231.45	$231.40
Purchase #5	$19.78	5.355%	$20.8392	$20.84	$20.85	$20.80
Purchase #6	$59.53	12.308%	$66.857	$66.86	$66.85	$66.90
Purchase #7	$44.97	7.590%	$48.3832	$48.38	$48.40	$48.40
7 purchase totals =	$554.15		$601.5732	$601.58	$601.65	$601.50