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	$188.50	12.206%	$211.5083	$211.51	$211.50	$211.50
Purchase #2	$31.69	9.432%	$34.679	$34.68	$34.70	$34.70
Purchase #3	$103.71	9.195%	$113.2461	$113.25	$113.25	$113.20
Purchase #4	$45.63	8.812%	$49.6509	$49.65	$49.65	$49.70
Purchase #5	$225.65	13.684%	$256.5279	$256.53	$256.55	$256.50
Purchase #6	$62.59	6.273%	$66.5163	$66.52	$66.50	$66.50
Purchase #7	$79.71	13.816%	$90.7227	$90.72	$90.70	$90.70
7 purchase totals =	$737.48		$822.8512	$822.86	$822.85	$822.80