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	$43.39	6.867%	$46.3696	$46.37	$46.35	$46.40
Purchase #2	$143.74	9.176%	$156.9296	$156.93	$156.95	$156.90
Purchase #3	$197.79	4.234%	$206.1644	$206.16	$206.15	$206.20
Purchase #4	$117.57	11.651%	$131.2681	$131.27	$131.25	$131.30
Purchase #5	$38.85	13.206%	$43.9805	$43.98	$44.00	$44.00
Purchase #6	$187.90	11.691%	$209.8674	$209.87	$209.85	$209.90
Purchase #7	$187.72	13.750%	$213.5315	$213.53	$213.55	$213.50
7 purchase totals =	$916.96		$1,008.1111	$1,008.11	$1,008.10	$1,008.20