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	$97.67	7.170%	$104.6729	$104.67	$104.65	$104.70
Purchase #2	$139.48	5.307%	$146.8822	$146.88	$146.90	$146.90
Purchase #3	$156.91	3.576%	$162.5211	$162.52	$162.50	$162.50
Purchase #4	$88.42	5.398%	$93.1929	$93.19	$93.20	$93.20
Purchase #5	$184.53	3.761%	$191.4702	$191.47	$191.45	$191.50
Purchase #6	$91.94	9.715%	$100.872	$100.87	$100.85	$100.90
Purchase #7	$59.83	12.827%	$67.5044	$67.50	$67.50	$67.50
7 purchase totals =	$818.78		$867.1157	$867.10	$867.05	$867.20