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	$195.50	7.636%	$210.4284	$210.43	$210.45	$210.40
Purchase #2	$149.84	5.763%	$158.4753	$158.48	$158.50	$158.50
Purchase #3	$107.38	3.843%	$111.5066	$111.51	$111.50	$111.50
Purchase #4	$103.79	12.292%	$116.5479	$116.55	$116.55	$116.50
Purchase #5	$27.71	8.285%	$30.0058	$30.01	$30.00	$30.00
Purchase #6	$231.29	10.567%	$255.7304	$255.73	$255.75	$255.70
Purchase #7	$20.39	8.719%	$22.1678	$22.17	$22.15	$22.20
7 purchase totals =	$835.90		$904.8622	$904.88	$904.90	$904.80