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	$44.42	9.363%	$48.579	$48.58	$48.60	$48.60
Purchase #2	$7.78	12.308%	$8.7376	$8.74	$8.75	$8.70
Purchase #3	$173.67	10.239%	$191.4521	$191.45	$191.45	$191.50
Purchase #4	$157.54	3.230%	$162.6285	$162.63	$162.65	$162.60
Purchase #5	$154.65	10.799%	$171.3507	$171.35	$171.35	$171.40
Purchase #6	$246.90	11.613%	$275.5725	$275.57	$275.55	$275.60
Purchase #7	$137.47	5.873%	$145.5436	$145.54	$145.55	$145.50
7 purchase totals =	$922.43		$1,003.8640	$1,003.86	$1,003.90	$1,003.90