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	$123.34	7.230%	$132.2575	$132.26	$132.25	$132.30
Purchase #2	$45.73	11.592%	$51.031	$51.03	$51.05	$51.00
Purchase #3	$204.57	8.788%	$222.5476	$222.55	$222.55	$222.50
Purchase #4	$21.64	13.583%	$24.5794	$24.58	$24.60	$24.60
Purchase #5	$100.53	6.102%	$106.6643	$106.66	$106.65	$106.70
Purchase #6	$57.87	7.383%	$62.1425	$62.14	$62.15	$62.10
Purchase #7	$186.64	5.437%	$196.7876	$196.79	$196.80	$196.80
7 purchase totals =	$740.32		$796.0099	$796.01	$796.05	$796.00