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	$107.79	3.531%	$111.5961	$111.60	$111.60	$111.60
Purchase #2	$83.76	12.386%	$94.1345	$94.13	$94.15	$94.10
Purchase #3	$37.50	13.160%	$42.435	$42.44	$42.45	$42.40
Purchase #4	$80.72	7.840%	$87.0484	$87.05	$87.05	$87.00
Purchase #5	$48.74	4.366%	$50.868	$50.87	$50.85	$50.90
Purchase #6	$187.39	6.579%	$199.7184	$199.72	$199.70	$199.70
Purchase #7	$114.85	4.243%	$119.7231	$119.72	$119.70	$119.70
7 purchase totals =	$660.75		$705.5235	$705.53	$705.50	$705.40