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	$34.49	4.850%	$36.1628	$36.16	$36.15	$36.20
Purchase #2	$134.96	4.146%	$140.5554	$140.56	$140.55	$140.60
Purchase #3	$54.83	10.692%	$60.6924	$60.69	$60.70	$60.70
Purchase #4	$81.68	10.473%	$90.2343	$90.23	$90.25	$90.20
Purchase #5	$150.45	5.359%	$158.5126	$158.51	$158.50	$158.50
Purchase #6	$190.63	13.497%	$216.3593	$216.36	$216.35	$216.40
Purchase #7	$205.30	10.123%	$226.0825	$226.08	$226.10	$226.10
7 purchase totals =	$852.34		$928.5993	$928.59	$928.60	$928.70