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	$131.84	10.339%	$145.4709	$145.47	$145.45	$145.50
Purchase #2	$80.45	8.739%	$87.4805	$87.48	$87.50	$87.50
Purchase #3	$35.32	11.545%	$39.3977	$39.40	$39.40	$39.40
Purchase #4	$102.37	11.803%	$114.4527	$114.45	$114.45	$114.50
Purchase #5	$53.46	5.646%	$56.4784	$56.48	$56.50	$56.50
Purchase #6	$18.45	11.223%	$20.5206	$20.52	$20.50	$20.50
Purchase #7	$244.31	6.293%	$259.6844	$259.68	$259.70	$259.70
7 purchase totals =	$666.20		$723.4852	$723.48	$723.50	$723.60