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	$87.69	6.714%	$93.5775	$93.58	$93.60	$93.60
Purchase #2	$38.75	8.491%	$42.0403	$42.04	$42.05	$42.00
Purchase #3	$101.89	10.428%	$112.5151	$112.52	$112.50	$112.50
Purchase #4	$243.51	7.434%	$261.6125	$261.61	$261.60	$261.60
Purchase #5	$136.27	9.392%	$149.0685	$149.07	$149.05	$149.10
Purchase #6	$33.85	10.171%	$37.2929	$37.29	$37.30	$37.30
Purchase #7	$7.27	11.740%	$8.1235	$8.12	$8.10	$8.10
7 purchase totals =	$649.23		$704.2303	$704.23	$704.20	$704.20