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	$200.55	13.744%	$228.1136	$228.11	$228.10	$228.10
Purchase #2	$200.56	4.160%	$208.9033	$208.90	$208.90	$208.90
Purchase #3	$113.35	7.868%	$122.2684	$122.27	$122.25	$122.30
Purchase #4	$86.73	4.443%	$90.5834	$90.58	$90.60	$90.60
Purchase #5	$96.67	12.262%	$108.5237	$108.52	$108.50	$108.50
Purchase #6	$247.57	10.542%	$273.6688	$273.67	$273.65	$273.70
Purchase #7	$32.98	7.846%	$35.5676	$35.57	$35.55	$35.60
7 purchase totals =	$978.41		$1,067.6288	$1,067.62	$1,067.55	$1,067.70