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	$106.37	13.478%	$120.7065	$120.71	$120.70	$120.70
Purchase #2	$204.47	8.329%	$221.5003	$221.50	$221.50	$221.50
Purchase #3	$85.95	13.342%	$97.4174	$97.42	$97.40	$97.40
Purchase #4	$17.88	8.176%	$19.3419	$19.34	$19.35	$19.30
Purchase #5	$180.60	11.250%	$200.9175	$200.92	$200.90	$200.90
Purchase #6	$204.67	13.300%	$231.8911	$231.89	$231.90	$231.90
Purchase #7	$165.55	12.282%	$185.8829	$185.88	$185.90	$185.90
7 purchase totals =	$965.49		$1,077.6576	$1,077.66	$1,077.65	$1,077.60