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	$142.65	13.283%	$161.5982	$161.60	$161.60	$161.60
Purchase #2	$119.28	5.668%	$126.0408	$126.04	$126.05	$126.00
Purchase #3	$206.61	3.541%	$213.9261	$213.93	$213.95	$213.90
Purchase #4	$83.69	8.173%	$90.53	$90.53	$90.55	$90.50
Purchase #5	$187.43	5.848%	$198.3909	$198.39	$198.40	$198.40
Purchase #6	$114.34	11.359%	$127.3279	$127.33	$127.35	$127.30
Purchase #7	$109.86	3.681%	$113.9039	$113.90	$113.90	$113.90
7 purchase totals =	$963.86		$1,031.7178	$1,031.72	$1,031.80	$1,031.60