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	$112.47	5.110%	$118.2172	$118.22	$118.20	$118.20
Purchase #2	$25.50	10.670%	$28.2209	$28.22	$28.20	$28.20
Purchase #3	$202.53	8.276%	$219.2914	$219.29	$219.30	$219.30
Purchase #4	$166.94	3.502%	$172.7862	$172.79	$172.80	$172.80
Purchase #5	$164.34	7.515%	$176.6902	$176.69	$176.70	$176.70
Purchase #6	$129.61	13.112%	$146.6045	$146.60	$146.60	$146.60
Purchase #7	$239.89	6.504%	$255.4924	$255.49	$255.50	$255.50
7 purchase totals =	$1,041.28		$1,117.3028	$1,117.30	$1,117.30	$1,117.30