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	$13.95	6.762%	$14.8933	$14.89	$14.90	$14.90
Purchase #2	$146.37	3.548%	$151.5632	$151.56	$151.55	$151.60
Purchase #3	$95.40	9.108%	$104.089	$104.09	$104.10	$104.10
Purchase #4	$175.85	5.308%	$185.1841	$185.18	$185.20	$185.20
Purchase #5	$58.42	10.422%	$64.5085	$64.51	$64.50	$64.50
Purchase #6	$81.74	13.654%	$92.9008	$92.90	$92.90	$92.90
Purchase #7	$139.52	12.646%	$157.1637	$157.16	$157.15	$157.20
7 purchase totals =	$711.25		$770.3026	$770.29	$770.30	$770.40