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	$218.70	3.246%	$225.799	$225.80	$225.80	$225.80
Purchase #2	$67.54	12.565%	$76.0264	$76.03	$76.05	$76.00
Purchase #3	$128.27	13.449%	$145.521	$145.52	$145.50	$145.50
Purchase #4	$198.90	11.216%	$221.2086	$221.21	$221.20	$221.20
Purchase #5	$129.67	10.190%	$142.8834	$142.88	$142.90	$142.90
Purchase #6	$154.87	8.221%	$167.6019	$167.60	$167.60	$167.60
Purchase #7	$217.64	12.520%	$244.8885	$244.89	$244.90	$244.90
7 purchase totals =	$1,115.59		$1,223.9288	$1,223.93	$1,223.95	$1,223.90