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	$226.77	9.504%	$248.3222	$248.32	$248.30	$248.30
Purchase #2	$112.46	9.803%	$123.4845	$123.48	$123.50	$123.50
Purchase #3	$200.97	10.754%	$222.5823	$222.58	$222.60	$222.60
Purchase #4	$137.95	5.587%	$145.6573	$145.66	$145.65	$145.70
Purchase #5	$123.46	9.402%	$135.0677	$135.07	$135.05	$135.10
Purchase #6	$138.40	6.577%	$147.5026	$147.50	$147.50	$147.50
Purchase #7	$35.67	13.811%	$40.5964	$40.60	$40.60	$40.60
7 purchase totals =	$975.68		$1,063.2130	$1,063.21	$1,063.20	$1,063.30