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	$208.67	6.796%	$222.8512	$222.85	$222.85	$222.90
Purchase #2	$153.50	10.183%	$169.1309	$169.13	$169.15	$169.10
Purchase #3	$35.54	12.327%	$39.921	$39.92	$39.90	$39.90
Purchase #4	$223.87	4.626%	$234.2262	$234.23	$234.25	$234.20
Purchase #5	$245.37	11.498%	$273.5826	$273.58	$273.60	$273.60
Purchase #6	$241.51	13.174%	$273.3265	$273.33	$273.35	$273.30
Purchase #7	$105.87	6.603%	$112.8606	$112.86	$112.85	$112.90
7 purchase totals =	$1,214.33		$1,325.8990	$1,325.90	$1,325.95	$1,325.90