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	$161.86	12.397%	$181.9258	$181.93	$181.95	$181.90
Purchase #2	$131.95	9.767%	$144.8376	$144.84	$144.85	$144.80
Purchase #3	$57.38	8.173%	$62.0697	$62.07	$62.05	$62.10
Purchase #4	$89.51	10.576%	$98.9766	$98.98	$99.00	$99.00
Purchase #5	$62.84	6.681%	$67.0383	$67.04	$67.05	$67.00
Purchase #6	$85.68	13.774%	$97.4816	$97.48	$97.50	$97.50
Purchase #7	$214.89	12.429%	$241.5987	$241.60	$241.60	$241.60
7 purchase totals =	$804.11		$893.9283	$893.94	$894.00	$893.90