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	$69.25	4.721%	$72.5193	$72.52	$72.50	$72.50
Purchase #2	$185.26	11.684%	$206.9058	$206.91	$206.90	$206.90
Purchase #3	$37.81	11.252%	$42.0644	$42.06	$42.05	$42.10
Purchase #4	$122.62	6.359%	$130.4174	$130.42	$130.40	$130.40
Purchase #5	$11.77	13.571%	$13.3673	$13.37	$13.35	$13.40
Purchase #6	$119.25	10.221%	$131.4385	$131.44	$131.45	$131.40
Purchase #7	$26.38	8.326%	$28.5764	$28.58	$28.60	$28.60
7 purchase totals =	$572.34		$625.2891	$625.30	$625.25	$625.30