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	$182.55	13.105%	$206.4732	$206.47	$206.45	$206.50
Purchase #2	$161.37	9.274%	$176.3355	$176.34	$176.35	$176.30
Purchase #3	$19.93	11.754%	$22.2726	$22.27	$22.25	$22.30
Purchase #4	$178.60	5.805%	$188.9677	$188.97	$188.95	$189.00
Purchase #5	$172.43	3.559%	$178.5668	$178.57	$178.55	$178.60
Purchase #6	$33.55	12.341%	$37.6904	$37.69	$37.70	$37.70
Purchase #7	$79.96	13.590%	$90.8266	$90.83	$90.85	$90.80
7 purchase totals =	$828.39		$901.1328	$901.14	$901.10	$901.20