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	$163.88	9.413%	$179.306	$179.31	$179.30	$179.30
Purchase #2	$57.60	12.862%	$65.0085	$65.01	$65.00	$65.00
Purchase #3	$27.40	3.744%	$28.4259	$28.43	$28.45	$28.40
Purchase #4	$64.88	11.249%	$72.1784	$72.18	$72.20	$72.20
Purchase #5	$29.38	9.761%	$32.2478	$32.25	$32.25	$32.20
Purchase #6	$25.44	7.829%	$27.4317	$27.43	$27.45	$27.40
Purchase #7	$59.81	9.800%	$65.6714	$65.67	$65.65	$65.70
7 purchase totals =	$428.39		$470.2697	$470.28	$470.30	$470.20