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	$33.63	11.681%	$37.5583	$37.56	$37.55	$37.60
Purchase #2	$169.69	12.474%	$190.8571	$190.86	$190.85	$190.90
Purchase #3	$110.39	11.845%	$123.4657	$123.47	$123.45	$123.50
Purchase #4	$194.30	12.504%	$218.5953	$218.60	$218.60	$218.60
Purchase #5	$123.67	7.552%	$133.0096	$133.01	$133.00	$133.00
Purchase #6	$240.67	4.197%	$250.7709	$250.77	$250.75	$250.80
Purchase #7	$13.45	10.267%	$14.8309	$14.83	$14.85	$14.80
7 purchase totals =	$885.80		$969.0878	$969.10	$969.05	$969.20