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	$118.27	10.775%	$131.0136	$131.01	$131.00	$131.00
Purchase #2	$245.35	4.428%	$256.2141	$256.21	$256.20	$256.20
Purchase #3	$98.72	5.811%	$104.4566	$104.46	$104.45	$104.50
Purchase #4	$142.71	13.862%	$162.4925	$162.49	$162.50	$162.50
Purchase #5	$33.51	8.852%	$36.4763	$36.48	$36.50	$36.50
Purchase #6	$85.46	8.547%	$92.7643	$92.76	$92.75	$92.80
Purchase #7	$214.35	7.333%	$230.0683	$230.07	$230.05	$230.10
7 purchase totals =	$938.37		$1,013.4857	$1,013.48	$1,013.45	$1,013.60