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	$40.38	10.342%	$44.5561	$44.56	$44.55	$44.60
Purchase #2	$225.58	4.185%	$235.0205	$235.02	$235.00	$235.00
Purchase #3	$44.78	8.514%	$48.5926	$48.59	$48.60	$48.60
Purchase #4	$127.71	7.470%	$137.2499	$137.25	$137.25	$137.20
Purchase #5	$158.74	8.319%	$171.9456	$171.95	$171.95	$171.90
Purchase #6	$210.96	6.619%	$224.9234	$224.92	$224.90	$224.90
Purchase #7	$136.56	13.295%	$154.7157	$154.72	$154.70	$154.70
7 purchase totals =	$944.71		$1,017.0038	$1,017.01	$1,016.95	$1,016.90