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	$212.51	12.195%	$238.4256	$238.43	$238.45	$238.40
Purchase #2	$106.93	10.776%	$118.4528	$118.45	$118.45	$118.50
Purchase #3	$67.33	5.129%	$70.7834	$70.78	$70.80	$70.80
Purchase #4	$132.63	3.279%	$136.9789	$136.98	$137.00	$137.00
Purchase #5	$83.50	8.418%	$90.529	$90.53	$90.55	$90.50
Purchase #6	$77.95	3.514%	$80.6892	$80.69	$80.70	$80.70
Purchase #7	$10.77	4.397%	$11.2436	$11.24	$11.25	$11.20
7 purchase totals =	$691.62		$747.1025	$747.10	$747.20	$747.10