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	$185.91	8.836%	$202.337	$202.34	$202.35	$202.30
Purchase #2	$184.98	11.143%	$205.5923	$205.59	$205.60	$205.60
Purchase #3	$189.35	5.389%	$199.5541	$199.55	$199.55	$199.60
Purchase #4	$37.64	8.265%	$40.7509	$40.75	$40.75	$40.80
Purchase #5	$248.39	10.571%	$274.6473	$274.65	$274.65	$274.60
Purchase #6	$149.52	13.346%	$169.4749	$169.47	$169.45	$169.50
Purchase #7	$17.79	6.456%	$18.9385	$18.94	$18.95	$18.90
7 purchase totals =	$1,013.58		$1,111.2950	$1,111.29	$1,111.30	$1,111.30