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	$116.84	11.764%	$130.5851	$130.59	$130.60	$130.60
Purchase #2	$15.51	6.757%	$16.558	$16.56	$16.55	$16.60
Purchase #3	$42.98	6.643%	$45.8352	$45.84	$45.85	$45.80
Purchase #4	$93.90	11.251%	$104.4647	$104.46	$104.45	$104.50
Purchase #5	$207.38	10.666%	$229.4992	$229.50	$229.50	$229.50
Purchase #6	$112.67	9.130%	$122.9568	$122.96	$122.95	$123.00
Purchase #7	$108.83	7.155%	$116.6168	$116.62	$116.60	$116.60
7 purchase totals =	$698.11		$766.5158	$766.53	$766.50	$766.60