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	$50.36	6.528%	$53.6475	$53.65	$53.65	$53.60
Purchase #2	$75.45	10.143%	$83.1029	$83.10	$83.10	$83.10
Purchase #3	$98.58	4.461%	$102.9777	$102.98	$103.00	$103.00
Purchase #4	$38.72	10.650%	$42.8437	$42.84	$42.85	$42.80
Purchase #5	$72.27	8.647%	$78.5192	$78.52	$78.50	$78.50
Purchase #6	$20.84	4.562%	$21.7907	$21.79	$21.80	$21.80
Purchase #7	$84.94	10.324%	$93.7092	$93.71	$93.70	$93.70
7 purchase totals =	$441.16		$476.5909	$476.59	$476.60	$476.50