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	$117.53	4.571%	$122.9023	$122.90	$122.90	$122.90
Purchase #2	$95.34	6.800%	$101.8231	$101.82	$101.80	$101.80
Purchase #3	$185.35	6.846%	$198.0391	$198.04	$198.05	$198.00
Purchase #4	$220.71	7.315%	$236.8549	$236.85	$236.85	$236.90
Purchase #5	$59.97	10.825%	$66.4618	$66.46	$66.45	$66.50
Purchase #6	$134.89	13.738%	$153.4212	$153.42	$153.40	$153.40
Purchase #7	$141.73	6.571%	$151.0431	$151.04	$151.05	$151.00
7 purchase totals =	$955.52		$1,030.5455	$1,030.53	$1,030.50	$1,030.50