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	$100.28	5.362%	$105.657	$105.66	$105.65	$105.70
Purchase #2	$29.95	9.709%	$32.8578	$32.86	$32.85	$32.90
Purchase #3	$66.89	10.465%	$73.89	$73.89	$73.90	$73.90
Purchase #4	$43.53	10.193%	$47.967	$47.97	$47.95	$48.00
Purchase #5	$47.69	10.175%	$52.5425	$52.54	$52.55	$52.50
Purchase #6	$91.49	7.720%	$98.553	$98.55	$98.55	$98.60
Purchase #7	$197.71	3.455%	$204.5409	$204.54	$204.55	$204.50
7 purchase totals =	$577.54		$616.0082	$616.01	$616.00	$616.10