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	$250.77	4.650%	$262.4308	$262.43	$262.45	$262.40
Purchase #2	$191.58	3.818%	$198.8945	$198.89	$198.90	$198.90
Purchase #3	$27.25	10.731%	$30.1742	$30.17	$30.15	$30.20
Purchase #4	$90.50	11.373%	$100.7926	$100.79	$100.80	$100.80
Purchase #5	$19.73	8.597%	$21.4262	$21.43	$21.45	$21.40
Purchase #6	$212.35	7.403%	$228.0703	$228.07	$228.05	$228.10
Purchase #7	$244.29	13.581%	$277.467	$277.47	$277.45	$277.50
7 purchase totals =	$1,036.47		$1,119.2556	$1,119.25	$1,119.25	$1,119.30