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	$142.67	6.649%	$152.1561	$152.16	$152.15	$152.20
Purchase #2	$93.92	12.262%	$105.4365	$105.44	$105.45	$105.40
Purchase #3	$124.37	4.720%	$130.2403	$130.24	$130.25	$130.20
Purchase #4	$101.38	11.841%	$113.3844	$113.38	$113.40	$113.40
Purchase #5	$140.57	13.613%	$159.7058	$159.71	$159.70	$159.70
Purchase #6	$88.59	12.522%	$99.6832	$99.68	$99.70	$99.70
Purchase #7	$88.51	3.436%	$91.5512	$91.55	$91.55	$91.60
7 purchase totals =	$780.01		$852.1575	$852.16	$852.20	$852.20