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	$145.35	8.573%	$157.8109	$157.81	$157.80	$157.80
Purchase #2	$151.27	10.312%	$166.869	$166.87	$166.85	$166.90
Purchase #3	$76.95	7.647%	$82.8344	$82.83	$82.85	$82.80
Purchase #4	$208.96	11.253%	$232.4743	$232.47	$232.45	$232.50
Purchase #5	$200.51	7.847%	$216.244	$216.24	$216.25	$216.20
Purchase #6	$66.47	7.232%	$71.2771	$71.28	$71.30	$71.30
Purchase #7	$142.72	7.533%	$153.4711	$153.47	$153.45	$153.50
7 purchase totals =	$992.23		$1,080.9808	$1,080.97	$1,080.95	$1,081.00