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	$59.39	12.602%	$66.8743	$66.87	$66.85	$66.90
Purchase #2	$140.51	10.808%	$155.6963	$155.70	$155.70	$155.70
Purchase #3	$13.48	10.500%	$14.8954	$14.90	$14.90	$14.90
Purchase #4	$72.73	8.523%	$78.9288	$78.93	$78.95	$78.90
Purchase #5	$30.61	6.326%	$32.5464	$32.55	$32.55	$32.50
Purchase #6	$104.86	4.530%	$109.6102	$109.61	$109.60	$109.60
Purchase #7	$149.90	4.303%	$156.3502	$156.35	$156.35	$156.40
7 purchase totals =	$571.48		$614.9016	$614.91	$614.90	$614.90