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	$85.96	6.271%	$91.3506	$91.35	$91.35	$91.40
Purchase #2	$155.82	6.338%	$165.6959	$165.70	$165.70	$165.70
Purchase #3	$231.30	10.293%	$255.1077	$255.11	$255.10	$255.10
Purchase #4	$161.85	3.597%	$167.6717	$167.67	$167.65	$167.70
Purchase #5	$136.55	5.749%	$144.4003	$144.40	$144.40	$144.40
Purchase #6	$30.74	5.776%	$32.5155	$32.52	$32.50	$32.50
Purchase #7	$250.29	6.414%	$266.3436	$266.34	$266.35	$266.30
7 purchase totals =	$1,052.51		$1,123.0853	$1,123.09	$1,123.05	$1,123.10