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	$76.80	7.446%	$82.5185	$82.52	$82.50	$82.50
Purchase #2	$63.34	3.174%	$65.3504	$65.35	$65.35	$65.40
Purchase #3	$88.46	7.650%	$95.2272	$95.23	$95.25	$95.20
Purchase #4	$187.58	13.404%	$212.7232	$212.72	$212.70	$212.70
Purchase #5	$130.87	4.689%	$137.0065	$137.01	$137.00	$137.00
Purchase #6	$214.28	13.178%	$242.5178	$242.52	$242.50	$242.50
Purchase #7	$96.30	9.804%	$105.7413	$105.74	$105.75	$105.70
7 purchase totals =	$857.63		$941.0849	$941.09	$941.05	$941.00