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	$164.92	7.448%	$177.2032	$177.20	$177.20	$177.20
Purchase #2	$210.40	13.715%	$239.2564	$239.26	$239.25	$239.30
Purchase #3	$72.80	12.167%	$81.6576	$81.66	$81.65	$81.70
Purchase #4	$38.57	4.468%	$40.2933	$40.29	$40.30	$40.30
Purchase #5	$54.68	9.303%	$59.7669	$59.77	$59.75	$59.80
Purchase #6	$99.53	11.810%	$111.2845	$111.28	$111.30	$111.30
Purchase #7	$68.28	5.109%	$71.7684	$71.77	$71.75	$71.80
7 purchase totals =	$709.18		$781.2303	$781.23	$781.20	$781.40