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	$145.35	11.755%	$162.4359	$162.44	$162.45	$162.40
Purchase #2	$94.68	11.141%	$105.2283	$105.23	$105.25	$105.20
Purchase #3	$217.78	9.484%	$238.4343	$238.43	$238.45	$238.40
Purchase #4	$18.70	7.632%	$20.1272	$20.13	$20.15	$20.10
Purchase #5	$241.46	7.610%	$259.8351	$259.84	$259.85	$259.80
Purchase #6	$62.96	5.645%	$66.5141	$66.51	$66.50	$66.50
Purchase #7	$172.53	10.323%	$190.3403	$190.34	$190.35	$190.30
7 purchase totals =	$953.46		$1,042.9152	$1,042.92	$1,043.00	$1,042.70