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	$14.76	3.300%	$15.2471	$15.25	$15.25	$15.20
Purchase #2	$206.54	4.688%	$216.2226	$216.22	$216.20	$216.20
Purchase #3	$42.75	7.339%	$45.8874	$45.89	$45.90	$45.90
Purchase #4	$235.57	8.152%	$254.7737	$254.77	$254.75	$254.80
Purchase #5	$40.38	13.638%	$45.887	$45.89	$45.90	$45.90
Purchase #6	$203.68	13.694%	$231.5719	$231.57	$231.55	$231.60
Purchase #7	$147.55	5.788%	$156.0902	$156.09	$156.10	$156.10
7 purchase totals =	$891.23		$965.6799	$965.68	$965.65	$965.70