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	$203.93	6.105%	$216.3799	$216.38	$216.40	$216.40
Purchase #2	$5.50	13.837%	$6.261	$6.26	$6.25	$6.30
Purchase #3	$46.26	8.855%	$50.3563	$50.36	$50.35	$50.40
Purchase #4	$97.78	8.198%	$105.796	$105.80	$105.80	$105.80
Purchase #5	$149.56	5.807%	$158.2449	$158.24	$158.25	$158.20
Purchase #6	$33.39	5.834%	$35.338	$35.34	$35.35	$35.30
Purchase #7	$50.34	10.192%	$55.4707	$55.47	$55.45	$55.50
7 purchase totals =	$586.76		$627.8468	$627.85	$627.85	$627.90