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	$43.67	7.375%	$46.8907	$46.89	$46.90	$46.90
Purchase #2	$237.57	12.571%	$267.4349	$267.43	$267.45	$267.40
Purchase #3	$12.47	7.699%	$13.4301	$13.43	$13.45	$13.40
Purchase #4	$5.48	9.441%	$5.9974	$6.00	$6.00	$6.00
Purchase #5	$228.72	5.147%	$240.4922	$240.49	$240.50	$240.50
Purchase #6	$99.37	3.257%	$102.6065	$102.61	$102.60	$102.60
Purchase #7	$82.29	9.471%	$90.0837	$90.08	$90.10	$90.10
7 purchase totals =	$709.57		$766.9355	$766.93	$767.00	$766.90