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	$99.38	4.153%	$103.5073	$103.51	$103.50	$103.50
Purchase #2	$75.96	13.143%	$85.9434	$85.94	$85.95	$85.90
Purchase #3	$82.45	11.184%	$91.6712	$91.67	$91.65	$91.70
Purchase #4	$225.28	8.816%	$245.1407	$245.14	$245.15	$245.10
Purchase #5	$112.59	13.333%	$127.6016	$127.60	$127.60	$127.60
Purchase #6	$109.89	3.311%	$113.5285	$113.53	$113.55	$113.50
Purchase #7	$101.71	12.752%	$114.6801	$114.68	$114.70	$114.70
7 purchase totals =	$807.26		$882.0728	$882.07	$882.10	$882.00