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	$62.44	11.392%	$69.5532	$69.55	$69.55	$69.60
Purchase #2	$118.54	10.631%	$131.142	$131.14	$131.15	$131.10
Purchase #3	$141.87	8.483%	$153.9048	$153.90	$153.90	$153.90
Purchase #4	$32.38	11.177%	$35.9991	$36.00	$36.00	$36.00
Purchase #5	$88.39	10.179%	$97.3872	$97.39	$97.40	$97.40
Purchase #6	$95.42	13.685%	$108.4782	$108.48	$108.50	$108.50
Purchase #7	$125.61	4.540%	$131.3127	$131.31	$131.30	$131.30
7 purchase totals =	$664.65		$727.7772	$727.77	$727.80	$727.80