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	$222.89	9.118%	$243.2131	$243.21	$243.20	$243.20
Purchase #2	$145.87	6.439%	$155.2626	$155.26	$155.25	$155.30
Purchase #3	$144.81	6.452%	$154.1531	$154.15	$154.15	$154.20
Purchase #4	$42.73	6.170%	$45.3664	$45.37	$45.35	$45.40
Purchase #5	$209.77	7.592%	$225.6957	$225.70	$225.70	$225.70
Purchase #6	$102.60	6.676%	$109.4496	$109.45	$109.45	$109.40
Purchase #7	$31.34	3.202%	$32.3435	$32.34	$32.35	$32.30
7 purchase totals =	$900.01		$965.4840	$965.48	$965.45	$965.50