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	$152.25	10.664%	$168.4859	$168.49	$168.50	$168.50
Purchase #2	$31.37	10.217%	$34.5751	$34.58	$34.60	$34.60
Purchase #3	$157.31	7.572%	$169.2215	$169.22	$169.20	$169.20
Purchase #4	$94.48	9.357%	$103.3205	$103.32	$103.30	$103.30
Purchase #5	$87.62	3.409%	$90.607	$90.61	$90.60	$90.60
Purchase #6	$82.69	5.678%	$87.3851	$87.39	$87.40	$87.40
Purchase #7	$137.91	11.395%	$153.6248	$153.62	$153.60	$153.60
7 purchase totals =	$743.63		$807.2199	$807.23	$807.20	$807.20