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	$46.27	4.665%	$48.4285	$48.43	$48.45	$48.40
Purchase #2	$64.49	12.451%	$72.5196	$72.52	$72.50	$72.50
Purchase #3	$181.27	13.291%	$205.3626	$205.36	$205.35	$205.40
Purchase #4	$175.49	10.856%	$194.5412	$194.54	$194.55	$194.50
Purchase #5	$82.74	3.438%	$85.5846	$85.58	$85.60	$85.60
Purchase #6	$148.51	11.445%	$165.507	$165.51	$165.50	$165.50
Purchase #7	$76.54	5.833%	$81.0046	$81.00	$81.00	$81.00
7 purchase totals =	$775.31		$852.9481	$852.94	$852.95	$852.90