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	$137.61	7.588%	$148.0518	$148.05	$148.05	$148.10
Purchase #2	$172.43	11.127%	$191.6163	$191.62	$191.60	$191.60
Purchase #3	$155.77	3.664%	$161.4774	$161.48	$161.50	$161.50
Purchase #4	$250.54	10.378%	$276.541	$276.54	$276.55	$276.50
Purchase #5	$43.86	7.514%	$47.1556	$47.16	$47.15	$47.20
Purchase #6	$182.53	13.530%	$207.2263	$207.23	$207.25	$207.20
Purchase #7	$148.49	10.556%	$164.1646	$164.16	$164.15	$164.20
7 purchase totals =	$1,091.23		$1,196.2330	$1,196.24	$1,196.25	$1,196.30