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	$115.39	10.499%	$127.5048	$127.50	$127.50	$127.50
Purchase #2	$131.31	13.190%	$148.6298	$148.63	$148.65	$148.60
Purchase #3	$65.59	11.708%	$73.2693	$73.27	$73.25	$73.30
Purchase #4	$137.65	6.166%	$146.1375	$146.14	$146.15	$146.10
Purchase #5	$95.56	8.844%	$104.0113	$104.01	$104.00	$104.00
Purchase #6	$139.34	11.665%	$155.594	$155.59	$155.60	$155.60
Purchase #7	$68.39	11.301%	$76.1188	$76.12	$76.10	$76.10
7 purchase totals =	$753.23		$831.2655	$831.26	$831.25	$831.20