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	$216.32	13.402%	$245.3112	$245.31	$245.30	$245.30
Purchase #2	$29.82	5.690%	$31.5168	$31.52	$31.50	$31.50
Purchase #3	$76.68	8.144%	$82.9248	$82.92	$82.90	$82.90
Purchase #4	$30.61	10.646%	$33.8687	$33.87	$33.85	$33.90
Purchase #5	$205.29	3.302%	$212.0687	$212.07	$212.05	$212.10
Purchase #6	$248.60	3.581%	$257.5024	$257.50	$257.50	$257.50
Purchase #7	$92.72	12.768%	$104.5585	$104.56	$104.55	$104.60
7 purchase totals =	$900.04		$967.7511	$967.75	$967.65	$967.80