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	$244.53	4.252%	$254.9274	$254.93	$254.95	$254.90
Purchase #2	$109.47	8.611%	$118.8965	$118.90	$118.90	$118.90
Purchase #3	$138.38	8.741%	$150.4758	$150.48	$150.50	$150.50
Purchase #4	$101.31	11.137%	$112.5929	$112.59	$112.60	$112.60
Purchase #5	$88.35	9.826%	$97.0313	$97.03	$97.05	$97.00
Purchase #6	$40.94	12.443%	$46.0342	$46.03	$46.05	$46.00
Purchase #7	$79.35	12.273%	$89.0886	$89.09	$89.10	$89.10
7 purchase totals =	$802.33		$869.0467	$869.05	$869.15	$869.00