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	$185.74	13.870%	$211.5021	$211.50	$211.50	$211.50
Purchase #2	$103.37	8.821%	$112.4883	$112.49	$112.50	$112.50
Purchase #3	$69.33	13.226%	$78.4996	$78.50	$78.50	$78.50
Purchase #4	$164.96	13.124%	$186.6094	$186.61	$186.60	$186.60
Purchase #5	$218.56	11.375%	$243.4212	$243.42	$243.40	$243.40
Purchase #6	$228.78	11.387%	$254.8312	$254.83	$254.85	$254.80
Purchase #7	$214.63	10.666%	$237.5224	$237.52	$237.50	$237.50
7 purchase totals =	$1,185.37		$1,324.8742	$1,324.87	$1,324.85	$1,324.80