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	$240.55	11.250%	$267.6119	$267.61	$267.60	$267.60
Purchase #2	$167.42	12.236%	$187.9055	$187.91	$187.90	$187.90
Purchase #3	$55.62	7.626%	$59.8616	$59.86	$59.85	$59.90
Purchase #4	$6.69	13.448%	$7.5897	$7.59	$7.60	$7.60
Purchase #5	$62.47	7.597%	$67.2158	$67.22	$67.20	$67.20
Purchase #6	$217.45	4.381%	$226.9765	$226.98	$227.00	$227.00
Purchase #7	$102.65	11.709%	$114.6693	$114.67	$114.65	$114.70
7 purchase totals =	$852.85		$931.8303	$931.84	$931.80	$931.90