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	$243.26	8.715%	$264.4601	$264.46	$264.45	$264.50
Purchase #2	$199.46	4.661%	$208.7568	$208.76	$208.75	$208.80
Purchase #3	$52.81	12.349%	$59.3315	$59.33	$59.35	$59.30
Purchase #4	$122.51	3.560%	$126.8714	$126.87	$126.85	$126.90
Purchase #5	$21.89	6.625%	$23.3402	$23.34	$23.35	$23.30
Purchase #6	$141.86	10.476%	$156.7213	$156.72	$156.70	$156.70
Purchase #7	$109.48	6.583%	$116.6871	$116.69	$116.70	$116.70
7 purchase totals =	$891.27		$956.1684	$956.17	$956.15	$956.20