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	$108.93	7.624%	$117.2348	$117.23	$117.25	$117.20
Purchase #2	$158.28	4.245%	$164.999	$165.00	$165.00	$165.00
Purchase #3	$209.97	3.426%	$217.1636	$217.16	$217.15	$217.20
Purchase #4	$190.51	3.150%	$196.5111	$196.51	$196.50	$196.50
Purchase #5	$166.78	4.134%	$173.6747	$173.67	$173.65	$173.70
Purchase #6	$40.34	12.604%	$45.4245	$45.42	$45.40	$45.40
Purchase #7	$59.37	3.358%	$61.3636	$61.36	$61.35	$61.40
7 purchase totals =	$934.18		$976.3713	$976.35	$976.30	$976.40