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	$151.43	13.163%	$171.3627	$171.36	$171.35	$171.40
Purchase #2	$232.57	13.400%	$263.7344	$263.73	$263.75	$263.70
Purchase #3	$189.60	3.666%	$196.5507	$196.55	$196.55	$196.60
Purchase #4	$108.68	7.536%	$116.8701	$116.87	$116.85	$116.90
Purchase #5	$119.94	10.470%	$132.4977	$132.50	$132.50	$132.50
Purchase #6	$137.91	13.594%	$156.6575	$156.66	$156.65	$156.70
Purchase #7	$63.30	7.814%	$68.2463	$68.25	$68.25	$68.20
7 purchase totals =	$1,003.43		$1,105.9194	$1,105.92	$1,105.90	$1,106.00