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	$136.62	9.828%	$150.047	$150.05	$150.05	$150.00
Purchase #2	$76.44	9.673%	$83.834	$83.83	$83.85	$83.80
Purchase #3	$178.44	9.779%	$195.8896	$195.89	$195.90	$195.90
Purchase #4	$82.57	3.281%	$85.2791	$85.28	$85.30	$85.30
Purchase #5	$185.63	3.112%	$191.4068	$191.41	$191.40	$191.40
Purchase #6	$85.35	13.140%	$96.565	$96.57	$96.55	$96.60
Purchase #7	$103.55	12.812%	$116.8168	$116.82	$116.80	$116.80
7 purchase totals =	$848.60		$919.8383	$919.85	$919.85	$919.80