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	$105.63	12.204%	$118.5211	$118.52	$118.50	$118.50
Purchase #2	$172.32	10.861%	$191.0357	$191.04	$191.05	$191.00
Purchase #3	$101.90	7.388%	$109.4284	$109.43	$109.45	$109.40
Purchase #4	$33.30	5.263%	$35.0526	$35.05	$35.05	$35.10
Purchase #5	$162.87	9.225%	$177.8948	$177.89	$177.90	$177.90
Purchase #6	$212.83	6.638%	$226.9577	$226.96	$226.95	$227.00
Purchase #7	$241.97	6.465%	$257.6134	$257.61	$257.60	$257.60
7 purchase totals =	$1,030.82		$1,116.5037	$1,116.50	$1,116.50	$1,116.50