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	$146.79	3.661%	$152.164	$152.16	$152.15	$152.20
Purchase #2	$236.41	13.318%	$267.8951	$267.90	$267.90	$267.90
Purchase #3	$80.81	10.423%	$89.2328	$89.23	$89.25	$89.20
Purchase #4	$139.77	5.686%	$147.7173	$147.72	$147.70	$147.70
Purchase #5	$59.60	9.778%	$65.4277	$65.43	$65.45	$65.40
Purchase #6	$118.89	13.261%	$134.656	$134.66	$134.65	$134.70
Purchase #7	$87.89	7.505%	$94.4861	$94.49	$94.50	$94.50
7 purchase totals =	$870.16		$951.5790	$951.59	$951.60	$951.60