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	$134.91	5.804%	$142.7402	$142.74	$142.75	$142.70
Purchase #2	$67.37	7.757%	$72.5959	$72.60	$72.60	$72.60
Purchase #3	$242.73	4.283%	$253.1261	$253.13	$253.15	$253.10
Purchase #4	$241.51	13.735%	$274.6814	$274.68	$274.70	$274.70
Purchase #5	$230.87	8.512%	$250.5217	$250.52	$250.50	$250.50
Purchase #6	$21.62	5.829%	$22.8802	$22.88	$22.90	$22.90
Purchase #7	$172.72	5.795%	$182.7291	$182.73	$182.75	$182.70
7 purchase totals =	$1,111.73		$1,199.2746	$1,199.28	$1,199.35	$1,199.20