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	$95.47	13.740%	$108.5876	$108.59	$108.60	$108.60
Purchase #2	$248.40	13.286%	$281.4024	$281.40	$281.40	$281.40
Purchase #3	$217.39	10.550%	$240.3246	$240.32	$240.30	$240.30
Purchase #4	$247.89	7.643%	$266.8362	$266.84	$266.85	$266.80
Purchase #5	$150.57	4.593%	$157.4857	$157.49	$157.50	$157.50
Purchase #6	$188.62	4.389%	$196.8985	$196.90	$196.90	$196.90
Purchase #7	$152.67	4.258%	$159.1707	$159.17	$159.15	$159.20
7 purchase totals =	$1,301.01		$1,410.7057	$1,410.71	$1,410.70	$1,410.70