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	$152.38	13.649%	$173.1783	$173.18	$173.20	$173.20
Purchase #2	$161.50	11.629%	$180.2808	$180.28	$180.30	$180.30
Purchase #3	$123.53	6.735%	$131.8497	$131.85	$131.85	$131.80
Purchase #4	$209.76	12.723%	$236.4478	$236.45	$236.45	$236.40
Purchase #5	$73.95	13.179%	$83.6959	$83.70	$83.70	$83.70
Purchase #6	$120.71	13.677%	$137.2195	$137.22	$137.20	$137.20
Purchase #7	$18.89	6.833%	$20.1808	$20.18	$20.20	$20.20
7 purchase totals =	$860.72		$962.8528	$962.86	$962.90	$962.80