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	$86.89	6.371%	$92.4258	$92.43	$92.45	$92.40
Purchase #2	$87.62	12.663%	$98.7153	$98.72	$98.70	$98.70
Purchase #3	$187.62	9.617%	$205.6634	$205.66	$205.65	$205.70
Purchase #4	$92.61	11.531%	$103.2889	$103.29	$103.30	$103.30
Purchase #5	$12.84	3.651%	$13.3088	$13.31	$13.30	$13.30
Purchase #6	$213.32	11.773%	$238.4342	$238.43	$238.45	$238.40
Purchase #7	$73.78	11.854%	$82.5259	$82.53	$82.55	$82.50
7 purchase totals =	$754.68		$834.3623	$834.37	$834.40	$834.30