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	$91.94	13.470%	$104.3243	$104.32	$104.30	$104.30
Purchase #2	$116.63	6.207%	$123.8692	$123.87	$123.85	$123.90
Purchase #3	$129.89	5.523%	$137.0638	$137.06	$137.05	$137.10
Purchase #4	$226.44	6.562%	$241.299	$241.30	$241.30	$241.30
Purchase #5	$199.44	10.244%	$219.8706	$219.87	$219.85	$219.90
Purchase #6	$66.63	10.333%	$73.5149	$73.51	$73.50	$73.50
Purchase #7	$13.57	11.130%	$15.0803	$15.08	$15.10	$15.10
7 purchase totals =	$844.54		$915.0221	$915.01	$914.95	$915.10