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	$116.49	13.799%	$132.5645	$132.56	$132.55	$132.60
Purchase #2	$42.82	5.597%	$45.2166	$45.22	$45.20	$45.20
Purchase #3	$219.26	8.334%	$237.5331	$237.53	$237.55	$237.50
Purchase #4	$84.95	6.776%	$90.7062	$90.71	$90.70	$90.70
Purchase #5	$130.89	6.828%	$139.8272	$139.83	$139.85	$139.80
Purchase #6	$210.25	6.452%	$223.8153	$223.82	$223.80	$223.80
Purchase #7	$100.79	3.159%	$103.974	$103.97	$103.95	$104.00
7 purchase totals =	$905.45		$973.6369	$973.64	$973.60	$973.60