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	$121.92	4.296%	$127.1577	$127.16	$127.15	$127.20
Purchase #2	$149.60	11.499%	$166.8025	$166.80	$166.80	$166.80
Purchase #3	$85.42	5.708%	$90.2958	$90.30	$90.30	$90.30
Purchase #4	$135.69	4.154%	$141.3266	$141.33	$141.35	$141.30
Purchase #5	$182.32	9.166%	$199.0315	$199.03	$199.05	$199.00
Purchase #6	$168.76	9.720%	$185.1635	$185.16	$185.15	$185.20
Purchase #7	$29.56	5.646%	$31.229	$31.23	$31.25	$31.20
7 purchase totals =	$873.27		$941.0066	$941.01	$941.05	$941.00