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	$30.83	5.749%	$32.6024	$32.60	$32.60	$32.60
Purchase #2	$85.65	7.571%	$92.1346	$92.13	$92.15	$92.10
Purchase #3	$219.34	13.493%	$248.9355	$248.94	$248.95	$248.90
Purchase #4	$78.97	12.820%	$89.094	$89.09	$89.10	$89.10
Purchase #5	$7.67	6.127%	$8.1399	$8.14	$8.15	$8.10
Purchase #6	$83.50	5.509%	$88.1	$88.10	$88.10	$88.10
Purchase #7	$162.37	3.521%	$168.087	$168.09	$168.10	$168.10
7 purchase totals =	$668.33		$727.0934	$727.09	$727.15	$727.00