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	$217.38	12.246%	$244.0004	$244.00	$244.00	$244.00
Purchase #2	$105.95	3.131%	$109.2673	$109.27	$109.25	$109.30
Purchase #3	$163.25	7.201%	$175.0056	$175.01	$175.00	$175.00
Purchase #4	$19.59	5.138%	$20.5965	$20.60	$20.60	$20.60
Purchase #5	$85.38	5.764%	$90.3013	$90.30	$90.30	$90.30
Purchase #6	$199.79	8.747%	$217.2656	$217.27	$217.25	$217.30
Purchase #7	$45.76	10.135%	$50.3978	$50.40	$50.40	$50.40
7 purchase totals =	$837.10		$906.8345	$906.85	$906.80	$906.90