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	$37.85	10.348%	$41.7667	$41.77	$41.75	$41.80
Purchase #2	$250.51	12.357%	$281.4655	$281.47	$281.45	$281.50
Purchase #3	$44.49	6.308%	$47.2964	$47.30	$47.30	$47.30
Purchase #4	$242.69	7.499%	$260.8893	$260.89	$260.90	$260.90
Purchase #5	$109.66	13.584%	$124.5562	$124.56	$124.55	$124.60
Purchase #6	$164.81	5.507%	$173.8861	$173.89	$173.90	$173.90
Purchase #7	$107.84	10.803%	$119.49	$119.49	$119.50	$119.50
7 purchase totals =	$957.85		$1,049.3502	$1,049.37	$1,049.35	$1,049.50