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	$74.93	11.177%	$83.3049	$83.30	$83.30	$83.30
Purchase #2	$141.79	11.257%	$157.7513	$157.75	$157.75	$157.80
Purchase #3	$214.49	13.243%	$242.8949	$242.89	$242.90	$242.90
Purchase #4	$147.34	9.294%	$161.0338	$161.03	$161.05	$161.00
Purchase #5	$181.55	5.160%	$190.918	$190.92	$190.90	$190.90
Purchase #6	$83.49	8.651%	$90.7127	$90.71	$90.70	$90.70
Purchase #7	$96.42	7.752%	$103.8945	$103.89	$103.90	$103.90
7 purchase totals =	$940.01		$1,030.5101	$1,030.49	$1,030.50	$1,030.50