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	$237.94	10.809%	$263.6589	$263.66	$263.65	$263.70
Purchase #2	$135.83	10.529%	$150.1315	$150.13	$150.15	$150.10
Purchase #3	$81.52	10.478%	$90.0617	$90.06	$90.05	$90.10
Purchase #4	$178.81	13.628%	$203.1782	$203.18	$203.20	$203.20
Purchase #5	$123.89	12.590%	$139.4878	$139.49	$139.50	$139.50
Purchase #6	$232.74	7.574%	$250.3677	$250.37	$250.35	$250.40
Purchase #7	$138.47	4.313%	$144.4422	$144.44	$144.45	$144.40
7 purchase totals =	$1,129.20		$1,241.3280	$1,241.33	$1,241.35	$1,241.40