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	$74.96	13.775%	$85.2857	$85.29	$85.30	$85.30
Purchase #2	$73.76	12.681%	$83.1135	$83.11	$83.10	$83.10
Purchase #3	$20.96	10.142%	$23.0858	$23.09	$23.10	$23.10
Purchase #4	$59.37	10.408%	$65.5492	$65.55	$65.55	$65.50
Purchase #5	$33.69	12.552%	$37.9188	$37.92	$37.90	$37.90
Purchase #6	$172.33	11.563%	$192.2565	$192.26	$192.25	$192.30
Purchase #7	$135.89	3.418%	$140.5347	$140.53	$140.55	$140.50
7 purchase totals =	$570.96		$627.7442	$627.75	$627.75	$627.70