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	$190.34	4.777%	$199.4325	$199.43	$199.45	$199.40
Purchase #2	$119.63	10.246%	$131.8873	$131.89	$131.90	$131.90
Purchase #3	$86.28	5.744%	$91.2359	$91.24	$91.25	$91.20
Purchase #4	$75.51	7.573%	$81.2284	$81.23	$81.25	$81.20
Purchase #5	$52.60	12.453%	$59.1503	$59.15	$59.15	$59.20
Purchase #6	$38.38	6.446%	$40.854	$40.85	$40.85	$40.90
Purchase #7	$30.75	3.823%	$31.9256	$31.93	$31.95	$31.90
7 purchase totals =	$593.49		$635.7140	$635.72	$635.80	$635.70