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	$124.43	12.797%	$140.3533	$140.35	$140.35	$140.40
Purchase #2	$87.85	8.790%	$95.572	$95.57	$95.55	$95.60
Purchase #3	$49.52	8.689%	$53.8228	$53.82	$53.80	$53.80
Purchase #4	$65.81	7.723%	$70.8925	$70.89	$70.90	$70.90
Purchase #5	$49.79	12.513%	$56.0202	$56.02	$56.00	$56.00
Purchase #6	$172.89	13.350%	$195.9708	$195.97	$195.95	$196.00
Purchase #7	$115.81	6.569%	$123.4176	$123.42	$123.40	$123.40
7 purchase totals =	$666.10		$736.0492	$736.04	$735.95	$736.10