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	$73.82	11.777%	$82.5138	$82.51	$82.50	$82.50
Purchase #2	$7.51	5.845%	$7.949	$7.95	$7.95	$7.90
Purchase #3	$184.29	13.728%	$209.5893	$209.59	$209.60	$209.60
Purchase #4	$14.42	12.723%	$16.2547	$16.25	$16.25	$16.30
Purchase #5	$24.32	9.267%	$26.5737	$26.57	$26.55	$26.60
Purchase #6	$92.86	11.808%	$103.8249	$103.82	$103.80	$103.80
Purchase #7	$88.29	12.672%	$99.4781	$99.48	$99.50	$99.50
7 purchase totals =	$485.51		$546.1835	$546.17	$546.15	$546.20