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	$82.77	4.466%	$86.4665	$86.47	$86.45	$86.50
Purchase #2	$95.74	9.452%	$104.7893	$104.79	$104.80	$104.80
Purchase #3	$168.58	7.511%	$181.242	$181.24	$181.25	$181.20
Purchase #4	$75.67	10.402%	$83.5412	$83.54	$83.55	$83.50
Purchase #5	$144.90	13.207%	$164.0369	$164.04	$164.05	$164.00
Purchase #6	$127.52	9.393%	$139.498	$139.50	$139.50	$139.50
Purchase #7	$159.79	9.143%	$174.3996	$174.40	$174.40	$174.40
7 purchase totals =	$854.97		$933.9735	$933.98	$934.00	$933.90