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	$195.85	6.814%	$209.1952	$209.20	$209.20	$209.20
Purchase #2	$110.31	11.538%	$123.0376	$123.04	$123.05	$123.00
Purchase #3	$90.75	13.376%	$102.8887	$102.89	$102.90	$102.90
Purchase #4	$245.90	12.685%	$277.0924	$277.09	$277.10	$277.10
Purchase #5	$149.78	12.628%	$168.6942	$168.69	$168.70	$168.70
Purchase #6	$119.95	9.326%	$131.1365	$131.14	$131.15	$131.10
Purchase #7	$125.60	10.835%	$139.2088	$139.21	$139.20	$139.20
7 purchase totals =	$1,038.14		$1,151.2534	$1,151.26	$1,151.30	$1,151.20