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	$21.75	3.146%	$22.4343	$22.43	$22.45	$22.40
Purchase #2	$111.69	12.764%	$125.9461	$125.95	$125.95	$125.90
Purchase #3	$101.71	4.157%	$105.9381	$105.94	$105.95	$105.90
Purchase #4	$140.65	8.109%	$152.0553	$152.06	$152.05	$152.10
Purchase #5	$132.59	3.262%	$136.9151	$136.92	$136.90	$136.90
Purchase #6	$243.69	13.157%	$275.7523	$275.75	$275.75	$275.80
Purchase #7	$61.37	8.539%	$66.6104	$66.61	$66.60	$66.60
7 purchase totals =	$813.45		$885.6516	$885.66	$885.65	$885.60