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	$186.87	13.304%	$211.7312	$211.73	$211.75	$211.70
Purchase #2	$244.58	11.548%	$272.8241	$272.82	$272.80	$272.80
Purchase #3	$52.77	12.165%	$59.1895	$59.19	$59.20	$59.20
Purchase #4	$196.68	7.361%	$211.1576	$211.16	$211.15	$211.20
Purchase #5	$63.44	11.836%	$70.9488	$70.95	$70.95	$70.90
Purchase #6	$66.49	9.363%	$72.7155	$72.72	$72.70	$72.70
Purchase #7	$29.51	11.646%	$32.9467	$32.95	$32.95	$32.90
7 purchase totals =	$840.34		$931.5134	$931.52	$931.50	$931.40