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	$174.28	10.167%	$191.999	$192.00	$192.00	$192.00
Purchase #2	$241.26	8.311%	$261.3111	$261.31	$261.30	$261.30
Purchase #3	$68.49	13.684%	$77.8622	$77.86	$77.85	$77.90
Purchase #4	$182.35	3.465%	$188.6684	$188.67	$188.65	$188.70
Purchase #5	$168.46	10.473%	$186.1028	$186.10	$186.10	$186.10
Purchase #6	$136.53	10.264%	$150.5434	$150.54	$150.55	$150.50
Purchase #7	$89.86	10.548%	$99.3384	$99.34	$99.35	$99.30
7 purchase totals =	$1,061.23		$1,155.8253	$1,155.82	$1,155.80	$1,155.80