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	$177.89	5.503%	$187.6793	$187.68	$187.70	$187.70
Purchase #2	$206.34	11.218%	$229.4872	$229.49	$229.50	$229.50
Purchase #3	$93.31	13.256%	$105.6792	$105.68	$105.70	$105.70
Purchase #4	$39.48	9.619%	$43.2776	$43.28	$43.30	$43.30
Purchase #5	$175.42	5.821%	$185.6312	$185.63	$185.65	$185.60
Purchase #6	$169.30	3.509%	$175.2407	$175.24	$175.25	$175.20
Purchase #7	$33.78	11.355%	$37.6157	$37.62	$37.60	$37.60
7 purchase totals =	$895.52		$964.6109	$964.62	$964.70	$964.60