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	$240.76	6.300%	$255.9279	$255.93	$255.95	$255.90
Purchase #2	$94.69	3.320%	$97.8337	$97.83	$97.85	$97.80
Purchase #3	$7.85	8.593%	$8.5246	$8.52	$8.50	$8.50
Purchase #4	$203.68	10.186%	$224.4268	$224.43	$224.45	$224.40
Purchase #5	$102.60	10.417%	$113.2878	$113.29	$113.30	$113.30
Purchase #6	$41.73	4.262%	$43.5085	$43.51	$43.50	$43.50
Purchase #7	$135.38	6.418%	$144.0687	$144.07	$144.05	$144.10
7 purchase totals =	$826.69		$887.5780	$887.58	$887.60	$887.50