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	$225.33	11.290%	$250.7698	$250.77	$250.75	$250.80
Purchase #2	$23.86	4.107%	$24.8399	$24.84	$24.85	$24.80
Purchase #3	$105.35	5.741%	$111.3981	$111.40	$111.40	$111.40
Purchase #4	$37.57	5.302%	$39.562	$39.56	$39.55	$39.60
Purchase #5	$67.86	4.354%	$70.8146	$70.81	$70.80	$70.80
Purchase #6	$209.78	5.867%	$222.0878	$222.09	$222.10	$222.10
Purchase #7	$131.26	9.700%	$143.9922	$143.99	$144.00	$144.00
7 purchase totals =	$801.01		$863.4644	$863.46	$863.45	$863.50