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	$249.75	5.812%	$264.2655	$264.27	$264.25	$264.30
Purchase #2	$26.31	5.408%	$27.7328	$27.73	$27.75	$27.70
Purchase #3	$73.99	11.564%	$82.5462	$82.55	$82.55	$82.50
Purchase #4	$21.67	8.577%	$23.5286	$23.53	$23.55	$23.50
Purchase #5	$200.38	13.384%	$227.1989	$227.20	$227.20	$227.20
Purchase #6	$241.94	12.386%	$271.9067	$271.91	$271.90	$271.90
Purchase #7	$110.96	7.564%	$119.353	$119.35	$119.35	$119.40
7 purchase totals =	$925.00		$1,016.5317	$1,016.54	$1,016.55	$1,016.50