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	$235.29	7.286%	$252.4332	$252.43	$252.45	$252.40
Purchase #2	$170.48	6.467%	$181.5049	$181.50	$181.50	$181.50
Purchase #3	$83.88	9.109%	$91.5206	$91.52	$91.50	$91.50
Purchase #4	$200.29	5.518%	$211.342	$211.34	$211.35	$211.30
Purchase #5	$142.30	13.472%	$161.4707	$161.47	$161.45	$161.50
Purchase #6	$131.85	8.820%	$143.4792	$143.48	$143.50	$143.50
Purchase #7	$159.46	9.433%	$174.5019	$174.50	$174.50	$174.50
7 purchase totals =	$1,123.55		$1,216.2525	$1,216.24	$1,216.25	$1,216.20