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	$131.90	11.366%	$146.8918	$146.89	$146.90	$146.90
Purchase #2	$29.35	8.193%	$31.7546	$31.75	$31.75	$31.80
Purchase #3	$93.59	7.676%	$100.774	$100.77	$100.75	$100.80
Purchase #4	$32.82	4.218%	$34.2043	$34.20	$34.20	$34.20
Purchase #5	$98.57	13.467%	$111.8444	$111.84	$111.85	$111.80
Purchase #6	$89.60	3.513%	$92.7476	$92.75	$92.75	$92.70
Purchase #7	$170.79	7.112%	$182.9366	$182.94	$182.95	$182.90
7 purchase totals =	$646.62		$701.1533	$701.14	$701.15	$701.10