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	$39.52	10.221%	$43.5593	$43.56	$43.55	$43.60
Purchase #2	$168.47	9.154%	$183.8917	$183.89	$183.90	$183.90
Purchase #3	$208.59	11.221%	$231.9959	$232.00	$232.00	$232.00
Purchase #4	$228.35	11.746%	$255.172	$255.17	$255.15	$255.20
Purchase #5	$23.60	13.705%	$26.8344	$26.83	$26.85	$26.80
Purchase #6	$38.95	11.694%	$43.5048	$43.50	$43.50	$43.50
Purchase #7	$40.67	9.408%	$44.4962	$44.50	$44.50	$44.50
7 purchase totals =	$748.15		$829.4543	$829.45	$829.45	$829.50