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	$162.29	5.516%	$171.2419	$171.24	$171.25	$171.20
Purchase #2	$90.51	10.838%	$100.3195	$100.32	$100.30	$100.30
Purchase #3	$167.34	13.569%	$190.0464	$190.05	$190.05	$190.00
Purchase #4	$186.78	11.422%	$208.114	$208.11	$208.10	$208.10
Purchase #5	$101.80	13.452%	$115.4941	$115.49	$115.50	$115.50
Purchase #6	$141.30	8.254%	$152.9629	$152.96	$152.95	$153.00
Purchase #7	$85.33	10.827%	$94.5687	$94.57	$94.55	$94.60
7 purchase totals =	$935.35		$1,032.7475	$1,032.74	$1,032.70	$1,032.70