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	$113.86	3.185%	$117.4864	$117.49	$117.50	$117.50
Purchase #2	$71.73	4.309%	$74.8208	$74.82	$74.80	$74.80
Purchase #3	$137.61	4.719%	$144.1038	$144.10	$144.10	$144.10
Purchase #4	$200.89	4.199%	$209.3254	$209.33	$209.35	$209.30
Purchase #5	$144.74	9.548%	$158.5598	$158.56	$158.55	$158.60
Purchase #6	$120.53	5.754%	$127.4653	$127.47	$127.45	$127.50
Purchase #7	$181.66	11.849%	$203.1849	$203.18	$203.20	$203.20
7 purchase totals =	$971.02		$1,034.9464	$1,034.95	$1,034.95	$1,035.00