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	$44.96	13.312%	$50.9451	$50.95	$50.95	$50.90
Purchase #2	$141.46	12.795%	$159.5598	$159.56	$159.55	$159.60
Purchase #3	$206.61	10.298%	$227.8867	$227.89	$227.90	$227.90
Purchase #4	$137.59	8.643%	$149.4819	$149.48	$149.50	$149.50
Purchase #5	$180.62	5.780%	$191.0598	$191.06	$191.05	$191.10
Purchase #6	$38.97	9.437%	$42.6476	$42.65	$42.65	$42.60
Purchase #7	$123.74	3.421%	$127.9731	$127.97	$127.95	$128.00
7 purchase totals =	$873.95		$949.5540	$949.56	$949.55	$949.60