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	$216.52	11.547%	$241.5216	$241.52	$241.50	$241.50
Purchase #2	$182.38	8.856%	$198.5316	$198.53	$198.55	$198.50
Purchase #3	$32.94	6.411%	$35.0518	$35.05	$35.05	$35.10
Purchase #4	$81.81	9.704%	$89.7488	$89.75	$89.75	$89.70
Purchase #5	$10.83	12.832%	$12.2197	$12.22	$12.20	$12.20
Purchase #6	$213.72	13.492%	$242.5551	$242.56	$242.55	$242.60
Purchase #7	$94.55	8.372%	$102.4657	$102.47	$102.45	$102.50
7 purchase totals =	$832.75		$922.0943	$922.10	$922.05	$922.10