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	$122.57	7.820%	$132.155	$132.16	$132.15	$132.20
Purchase #2	$100.76	11.137%	$111.9816	$111.98	$112.00	$112.00
Purchase #3	$154.49	6.355%	$164.3078	$164.31	$164.30	$164.30
Purchase #4	$30.88	3.438%	$31.9417	$31.94	$31.95	$31.90
Purchase #5	$56.60	4.734%	$59.2794	$59.28	$59.30	$59.30
Purchase #6	$233.47	3.192%	$240.9224	$240.92	$240.90	$240.90
Purchase #7	$182.73	12.452%	$205.4835	$205.48	$205.50	$205.50
7 purchase totals =	$881.50		$946.0714	$946.07	$946.10	$946.10