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	$14.25	7.619%	$15.3357	$15.34	$15.35	$15.30
Purchase #2	$146.33	3.688%	$151.7267	$151.73	$151.75	$151.70
Purchase #3	$80.47	13.166%	$91.0647	$91.06	$91.05	$91.10
Purchase #4	$203.29	11.777%	$227.2315	$227.23	$227.25	$227.20
Purchase #5	$116.36	8.618%	$126.3879	$126.39	$126.40	$126.40
Purchase #6	$147.45	3.345%	$152.3822	$152.38	$152.40	$152.40
Purchase #7	$172.59	10.321%	$190.403	$190.40	$190.40	$190.40
7 purchase totals =	$880.74		$954.5317	$954.53	$954.60	$954.50