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	$129.86	10.656%	$143.6979	$143.70	$143.70	$143.70
Purchase #2	$217.39	13.523%	$246.7876	$246.79	$246.80	$246.80
Purchase #3	$30.30	6.628%	$32.3083	$32.31	$32.30	$32.30
Purchase #4	$223.65	6.804%	$238.8671	$238.87	$238.85	$238.90
Purchase #5	$228.71	3.838%	$237.4879	$237.49	$237.50	$237.50
Purchase #6	$51.78	10.565%	$57.2506	$57.25	$57.25	$57.30
Purchase #7	$88.69	12.622%	$99.8845	$99.88	$99.90	$99.90
7 purchase totals =	$970.38		$1,056.2839	$1,056.29	$1,056.30	$1,056.40