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	$114.33	4.823%	$119.8441	$119.84	$119.85	$119.80
Purchase #2	$84.70	10.151%	$93.2979	$93.30	$93.30	$93.30
Purchase #3	$43.45	13.527%	$49.3275	$49.33	$49.35	$49.30
Purchase #4	$171.51	11.615%	$191.4309	$191.43	$191.45	$191.40
Purchase #5	$140.84	6.219%	$149.5988	$149.60	$149.60	$149.60
Purchase #6	$53.82	10.774%	$59.6186	$59.62	$59.60	$59.60
Purchase #7	$18.90	8.725%	$20.549	$20.55	$20.55	$20.50
7 purchase totals =	$627.55		$683.6668	$683.67	$683.70	$683.50