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	$201.42	11.160%	$223.8985	$223.90	$223.90	$223.90
Purchase #2	$159.96	13.475%	$181.5146	$181.51	$181.50	$181.50
Purchase #3	$219.87	5.428%	$231.8045	$231.80	$231.80	$231.80
Purchase #4	$184.41	3.244%	$190.3923	$190.39	$190.40	$190.40
Purchase #5	$21.54	10.310%	$23.7608	$23.76	$23.75	$23.80
Purchase #6	$241.46	13.720%	$274.5883	$274.59	$274.60	$274.60
Purchase #7	$90.36	12.225%	$101.4065	$101.41	$101.40	$101.40
7 purchase totals =	$1,119.02		$1,227.3655	$1,227.36	$1,227.35	$1,227.40