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	$208.35	6.576%	$222.0511	$222.05	$222.05	$222.10
Purchase #2	$62.62	6.679%	$66.8024	$66.80	$66.80	$66.80
Purchase #3	$18.47	11.347%	$20.5658	$20.57	$20.55	$20.60
Purchase #4	$228.90	13.850%	$260.6027	$260.60	$260.60	$260.60
Purchase #5	$112.79	13.148%	$127.6196	$127.62	$127.60	$127.60
Purchase #6	$214.45	13.405%	$243.197	$243.20	$243.20	$243.20
Purchase #7	$135.67	11.709%	$151.5556	$151.56	$151.55	$151.60
7 purchase totals =	$981.25		$1,092.3942	$1,092.40	$1,092.35	$1,092.50