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	$139.96	12.439%	$157.3696	$157.37	$157.35	$157.40
Purchase #2	$241.27	5.707%	$255.0393	$255.04	$255.05	$255.00
Purchase #3	$31.29	3.711%	$32.4512	$32.45	$32.45	$32.50
Purchase #4	$177.41	5.788%	$187.6785	$187.68	$187.70	$187.70
Purchase #5	$80.70	11.170%	$89.7142	$89.71	$89.70	$89.70
Purchase #6	$199.86	7.517%	$214.8835	$214.88	$214.90	$214.90
Purchase #7	$156.49	11.477%	$174.4504	$174.45	$174.45	$174.50
7 purchase totals =	$1,026.98		$1,111.5867	$1,111.58	$1,111.60	$1,111.70