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	$227.25	3.159%	$234.4288	$234.43	$234.45	$234.40
Purchase #2	$29.77	9.470%	$32.5892	$32.59	$32.60	$32.60
Purchase #3	$35.85	7.638%	$38.5882	$38.59	$38.60	$38.60
Purchase #4	$218.29	6.660%	$232.8281	$232.83	$232.85	$232.80
Purchase #5	$47.76	8.742%	$51.9352	$51.94	$51.95	$51.90
Purchase #6	$128.69	10.260%	$141.8936	$141.89	$141.90	$141.90
Purchase #7	$113.64	11.405%	$126.6006	$126.60	$126.60	$126.60
7 purchase totals =	$801.25		$858.8637	$858.87	$858.95	$858.80