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	$219.66	5.446%	$231.6227	$231.62	$231.60	$231.60
Purchase #2	$32.31	10.235%	$35.6169	$35.62	$35.60	$35.60
Purchase #3	$203.69	5.809%	$215.5224	$215.52	$215.50	$215.50
Purchase #4	$10.35	8.695%	$11.2499	$11.25	$11.25	$11.20
Purchase #5	$210.50	3.812%	$218.5243	$218.52	$218.50	$218.50
Purchase #6	$82.45	10.164%	$90.8302	$90.83	$90.85	$90.80
Purchase #7	$76.59	13.622%	$87.0231	$87.02	$87.00	$87.00
7 purchase totals =	$835.55		$890.3895	$890.38	$890.30	$890.20