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	$126.45	4.759%	$132.4678	$132.47	$132.45	$132.50
Purchase #2	$168.88	4.712%	$176.8376	$176.84	$176.85	$176.80
Purchase #3	$92.94	4.295%	$96.9318	$96.93	$96.95	$96.90
Purchase #4	$37.36	9.483%	$40.9028	$40.90	$40.90	$40.90
Purchase #5	$41.48	3.423%	$42.8999	$42.90	$42.90	$42.90
Purchase #6	$39.36	6.275%	$41.8298	$41.83	$41.85	$41.80
Purchase #7	$92.51	11.571%	$103.2143	$103.21	$103.20	$103.20
7 purchase totals =	$598.98		$635.0840	$635.08	$635.10	$635.00