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	$228.50	5.311%	$240.6356	$240.64	$240.65	$240.60
Purchase #2	$29.78	4.681%	$31.174	$31.17	$31.15	$31.20
Purchase #3	$45.82	12.211%	$51.4151	$51.42	$51.40	$51.40
Purchase #4	$19.90	7.456%	$21.3837	$21.38	$21.40	$21.40
Purchase #5	$25.56	7.308%	$27.4279	$27.43	$27.45	$27.40
Purchase #6	$169.71	9.711%	$186.1905	$186.19	$186.20	$186.20
Purchase #7	$210.37	7.742%	$226.6568	$226.66	$226.65	$226.70
7 purchase totals =	$729.64		$784.8836	$784.89	$784.90	$784.90