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	$122.33	4.782%	$128.1798	$128.18	$128.20	$128.20
Purchase #2	$141.60	4.201%	$147.5486	$147.55	$147.55	$147.50
Purchase #3	$42.43	9.620%	$46.5118	$46.51	$46.50	$46.50
Purchase #4	$76.55	11.810%	$85.5906	$85.59	$85.60	$85.60
Purchase #5	$62.32	11.336%	$69.3846	$69.38	$69.40	$69.40
Purchase #6	$11.71	11.768%	$13.088	$13.09	$13.10	$13.10
Purchase #7	$199.73	10.858%	$221.4167	$221.42	$221.40	$221.40
7 purchase totals =	$656.67		$711.7201	$711.72	$711.75	$711.70