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	$62.55	7.842%	$67.4552	$67.46	$67.45	$67.50
Purchase #2	$178.43	6.606%	$190.2171	$190.22	$190.20	$190.20
Purchase #3	$155.32	6.806%	$165.8911	$165.89	$165.90	$165.90
Purchase #4	$158.62	6.518%	$168.9589	$168.96	$168.95	$169.00
Purchase #5	$180.55	8.841%	$196.5124	$196.51	$196.50	$196.50
Purchase #6	$34.66	11.233%	$38.5534	$38.55	$38.55	$38.60
Purchase #7	$228.70	6.641%	$243.888	$243.89	$243.90	$243.90
7 purchase totals =	$998.83		$1,071.4761	$1,071.48	$1,071.45	$1,071.60