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	$10.31	4.855%	$10.8106	$10.81	$10.80	$10.80
Purchase #2	$36.72	6.134%	$38.9724	$38.97	$38.95	$39.00
Purchase #3	$225.79	9.126%	$246.3956	$246.40	$246.40	$246.40
Purchase #4	$61.89	4.227%	$64.5061	$64.51	$64.50	$64.50
Purchase #5	$19.41	11.484%	$21.639	$21.64	$21.65	$21.60
Purchase #6	$59.27	5.479%	$62.5174	$62.52	$62.50	$62.50
Purchase #7	$13.91	13.641%	$15.8075	$15.81	$15.80	$15.80
7 purchase totals =	$427.30		$460.6486	$460.66	$460.60	$460.60