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	$126.59	3.721%	$131.3004	$131.30	$131.30	$131.30
Purchase #2	$67.40	10.527%	$74.4952	$74.50	$74.50	$74.50
Purchase #3	$226.75	5.175%	$238.4843	$238.48	$238.50	$238.50
Purchase #4	$143.64	5.509%	$151.5531	$151.55	$151.55	$151.60
Purchase #5	$156.90	7.234%	$168.2501	$168.25	$168.25	$168.30
Purchase #6	$130.60	4.709%	$136.75	$136.75	$136.75	$136.80
Purchase #7	$140.86	3.659%	$146.0141	$146.01	$146.00	$146.00
7 purchase totals =	$992.74		$1,046.8472	$1,046.84	$1,046.85	$1,047.00