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	$138.51	10.705%	$153.3375	$153.34	$153.35	$153.30
Purchase #2	$14.28	9.222%	$15.5969	$15.60	$15.60	$15.60
Purchase #3	$19.60	4.384%	$20.4593	$20.46	$20.45	$20.50
Purchase #4	$17.66	8.166%	$19.1021	$19.10	$19.10	$19.10
Purchase #5	$53.36	3.189%	$55.0617	$55.06	$55.05	$55.10
Purchase #6	$227.35	12.836%	$256.5326	$256.53	$256.55	$256.50
Purchase #7	$135.60	8.650%	$147.3294	$147.33	$147.35	$147.30
7 purchase totals =	$606.36		$667.4195	$667.42	$667.45	$667.40