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	$39.45	11.402%	$43.9481	$43.95	$43.95	$43.90
Purchase #2	$122.82	4.226%	$128.0104	$128.01	$128.00	$128.00
Purchase #3	$243.74	3.582%	$252.4708	$252.47	$252.45	$252.50
Purchase #4	$30.60	4.126%	$31.8626	$31.86	$31.85	$31.90
Purchase #5	$103.30	6.224%	$109.7294	$109.73	$109.75	$109.70
Purchase #6	$36.50	11.577%	$40.7256	$40.73	$40.75	$40.70
Purchase #7	$109.73	8.582%	$119.147	$119.15	$119.15	$119.10
7 purchase totals =	$686.14		$725.8939	$725.90	$725.90	$725.80