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	$64.54	12.576%	$72.6566	$72.66	$72.65	$72.70
Purchase #2	$172.72	4.153%	$179.8931	$179.89	$179.90	$179.90
Purchase #3	$113.67	9.854%	$124.871	$124.87	$124.85	$124.90
Purchase #4	$227.30	4.500%	$237.5285	$237.53	$237.55	$237.50
Purchase #5	$244.60	10.551%	$270.4077	$270.41	$270.40	$270.40
Purchase #6	$174.44	9.214%	$190.5129	$190.51	$190.50	$190.50
Purchase #7	$108.80	8.846%	$118.4244	$118.42	$118.40	$118.40
7 purchase totals =	$1,106.07		$1,194.2942	$1,194.29	$1,194.25	$1,194.30