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	$199.76	13.822%	$227.3708	$227.37	$227.35	$227.40
Purchase #2	$101.84	11.198%	$113.244	$113.24	$113.25	$113.20
Purchase #3	$18.76	12.707%	$21.1438	$21.14	$21.15	$21.10
Purchase #4	$39.31	6.294%	$41.7842	$41.78	$41.80	$41.80
Purchase #5	$82.71	9.237%	$90.3499	$90.35	$90.35	$90.30
Purchase #6	$241.94	5.486%	$255.2128	$255.21	$255.20	$255.20
Purchase #7	$177.87	12.605%	$200.2905	$200.29	$200.30	$200.30
7 purchase totals =	$862.19		$949.3960	$949.38	$949.40	$949.30