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	$130.48	13.290%	$147.8208	$147.82	$147.80	$147.80
Purchase #2	$141.45	12.231%	$158.7507	$158.75	$158.75	$158.80
Purchase #3	$109.57	6.379%	$116.5595	$116.56	$116.55	$116.60
Purchase #4	$166.52	12.678%	$187.6314	$187.63	$187.65	$187.60
Purchase #5	$12.50	7.603%	$13.4504	$13.45	$13.45	$13.50
Purchase #6	$85.52	5.476%	$90.2031	$90.20	$90.20	$90.20
Purchase #7	$35.25	10.138%	$38.8236	$38.82	$38.80	$38.80
7 purchase totals =	$681.29		$753.2395	$753.23	$753.20	$753.30