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	$184.57	6.380%	$196.3456	$196.35	$196.35	$196.30
Purchase #2	$200.97	8.492%	$218.0364	$218.04	$218.05	$218.00
Purchase #3	$78.39	12.113%	$87.8854	$87.89	$87.90	$87.90
Purchase #4	$201.82	7.544%	$217.0453	$217.05	$217.05	$217.00
Purchase #5	$241.81	5.666%	$255.511	$255.51	$255.50	$255.50
Purchase #6	$191.38	7.372%	$205.4885	$205.49	$205.50	$205.50
Purchase #7	$80.57	6.334%	$85.6733	$85.67	$85.65	$85.70
7 purchase totals =	$1,179.51		$1,265.9855	$1,266.00	$1,266.00	$1,265.90