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	$157.53	13.825%	$179.3085	$179.31	$179.30	$179.30
Purchase #2	$45.67	6.188%	$48.4961	$48.50	$48.50	$48.50
Purchase #3	$100.72	12.803%	$113.6152	$113.62	$113.60	$113.60
Purchase #4	$35.48	13.431%	$40.2453	$40.25	$40.25	$40.20
Purchase #5	$183.85	6.326%	$195.4804	$195.48	$195.50	$195.50
Purchase #6	$110.47	12.536%	$124.3185	$124.32	$124.30	$124.30
Purchase #7	$37.99	12.294%	$42.6605	$42.66	$42.65	$42.70
7 purchase totals =	$671.71		$744.1245	$744.14	$744.10	$744.10