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	$131.81	9.732%	$144.6377	$144.64	$144.65	$144.60
Purchase #2	$113.27	9.388%	$123.9038	$123.90	$123.90	$123.90
Purchase #3	$230.44	5.713%	$243.605	$243.61	$243.60	$243.60
Purchase #4	$235.70	6.383%	$250.7447	$250.74	$250.75	$250.70
Purchase #5	$32.50	9.576%	$35.6122	$35.61	$35.60	$35.60
Purchase #6	$167.64	7.519%	$180.2449	$180.24	$180.25	$180.20
Purchase #7	$13.29	9.841%	$14.5979	$14.60	$14.60	$14.60
7 purchase totals =	$924.65		$993.3462	$993.34	$993.35	$993.20