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	$235.54	12.706%	$265.4677	$265.47	$265.45	$265.50
Purchase #2	$30.74	3.596%	$31.8454	$31.85	$31.85	$31.80
Purchase #3	$77.63	12.800%	$87.5666	$87.57	$87.55	$87.60
Purchase #4	$57.61	6.453%	$61.3276	$61.33	$61.35	$61.30
Purchase #5	$246.55	3.677%	$255.6156	$255.62	$255.60	$255.60
Purchase #6	$56.83	7.309%	$60.9837	$60.98	$61.00	$61.00
Purchase #7	$59.25	5.441%	$62.4738	$62.47	$62.45	$62.50
7 purchase totals =	$764.15		$825.2804	$825.29	$825.25	$825.30