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	$90.69	4.515%	$94.7847	$94.78	$94.80	$94.80
Purchase #2	$168.86	13.235%	$191.2086	$191.21	$191.20	$191.20
Purchase #3	$15.99	13.355%	$18.1255	$18.13	$18.15	$18.10
Purchase #4	$31.55	4.812%	$33.0682	$33.07	$33.05	$33.10
Purchase #5	$112.57	9.472%	$123.2326	$123.23	$123.25	$123.20
Purchase #6	$63.51	8.384%	$68.8347	$68.83	$68.85	$68.80
Purchase #7	$154.37	12.257%	$173.2911	$173.29	$173.30	$173.30
7 purchase totals =	$637.54		$702.5454	$702.54	$702.60	$702.50