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	$116.96	12.564%	$131.6549	$131.65	$131.65	$131.70
Purchase #2	$139.68	11.770%	$156.1203	$156.12	$156.10	$156.10
Purchase #3	$35.43	7.794%	$38.1914	$38.19	$38.20	$38.20
Purchase #4	$116.79	13.635%	$132.7143	$132.71	$132.70	$132.70
Purchase #5	$69.78	3.606%	$72.2963	$72.30	$72.30	$72.30
Purchase #6	$157.96	6.458%	$168.1611	$168.16	$168.15	$168.20
Purchase #7	$114.32	7.726%	$123.1524	$123.15	$123.15	$123.20
7 purchase totals =	$750.92		$822.2907	$822.28	$822.25	$822.40