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	$217.59	3.520%	$225.2492	$225.25	$225.25	$225.20
Purchase #2	$226.90	12.189%	$254.5568	$254.56	$254.55	$254.60
Purchase #3	$38.77	4.564%	$40.5395	$40.54	$40.55	$40.50
Purchase #4	$243.48	7.553%	$261.87	$261.87	$261.85	$261.90
Purchase #5	$142.32	9.757%	$156.2062	$156.21	$156.20	$156.20
Purchase #6	$80.35	9.800%	$88.2243	$88.22	$88.20	$88.20
Purchase #7	$62.79	11.304%	$69.8878	$69.89	$69.90	$69.90
7 purchase totals =	$1,012.20		$1,096.5338	$1,096.54	$1,096.50	$1,096.50