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	$188.96	13.235%	$213.9689	$213.97	$213.95	$214.00
Purchase #2	$91.82	13.301%	$104.033	$104.03	$104.05	$104.00
Purchase #3	$114.94	7.789%	$123.8927	$123.89	$123.90	$123.90
Purchase #4	$218.69	11.556%	$243.9618	$243.96	$243.95	$244.00
Purchase #5	$148.89	13.796%	$169.4309	$169.43	$169.45	$169.40
Purchase #6	$69.68	8.319%	$75.4767	$75.48	$75.50	$75.50
Purchase #7	$92.37	9.227%	$100.893	$100.89	$100.90	$100.90
7 purchase totals =	$925.35		$1,031.6570	$1,031.65	$1,031.70	$1,031.70