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	$59.29	3.521%	$61.3776	$61.38	$61.40	$61.40
Purchase #2	$56.58	11.243%	$62.9413	$62.94	$62.95	$62.90
Purchase #3	$236.40	11.669%	$263.9855	$263.99	$264.00	$264.00
Purchase #4	$32.56	8.797%	$35.4243	$35.42	$35.40	$35.40
Purchase #5	$114.53	13.596%	$130.1015	$130.10	$130.10	$130.10
Purchase #6	$146.60	5.310%	$154.3845	$154.38	$154.40	$154.40
Purchase #7	$170.76	10.155%	$188.1007	$188.10	$188.10	$188.10
7 purchase totals =	$816.72		$896.3154	$896.31	$896.35	$896.30