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	$111.31	12.103%	$124.7818	$124.78	$124.80	$124.80
Purchase #2	$65.81	7.692%	$70.8721	$70.87	$70.85	$70.90
Purchase #3	$12.69	5.128%	$13.3407	$13.34	$13.35	$13.30
Purchase #4	$231.95	12.857%	$261.7718	$261.77	$261.75	$261.80
Purchase #5	$96.57	5.837%	$102.2068	$102.21	$102.20	$102.20
Purchase #6	$76.56	8.267%	$82.8892	$82.89	$82.90	$82.90
Purchase #7	$37.52	3.839%	$38.9604	$38.96	$38.95	$39.00
7 purchase totals =	$632.41		$694.8228	$694.82	$694.80	$694.90