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	$227.67	13.522%	$258.4555	$258.46	$258.45	$258.50
Purchase #2	$201.34	12.542%	$226.5921	$226.59	$226.60	$226.60
Purchase #3	$209.47	10.662%	$231.8037	$231.80	$231.80	$231.80
Purchase #4	$25.54	7.657%	$27.4956	$27.50	$27.50	$27.50
Purchase #5	$132.66	8.599%	$144.0674	$144.07	$144.05	$144.10
Purchase #6	$35.90	13.649%	$40.8	$40.80	$40.80	$40.80
Purchase #7	$64.88	13.580%	$73.6907	$73.69	$73.70	$73.70
7 purchase totals =	$897.46		$1,002.9050	$1,002.91	$1,002.90	$1,003.00