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	$83.32	3.258%	$86.0346	$86.03	$86.05	$86.00
Purchase #2	$241.58	11.495%	$269.3496	$269.35	$269.35	$269.30
Purchase #3	$82.62	9.358%	$90.3516	$90.35	$90.35	$90.40
Purchase #4	$144.60	9.513%	$158.3558	$158.36	$158.35	$158.40
Purchase #5	$196.96	7.322%	$211.3814	$211.38	$211.40	$211.40
Purchase #6	$80.41	10.201%	$88.6126	$88.61	$88.60	$88.60
Purchase #7	$85.94	9.597%	$94.1877	$94.19	$94.20	$94.20
7 purchase totals =	$915.43		$998.2733	$998.27	$998.30	$998.30