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	$141.74	6.262%	$150.6158	$150.62	$150.60	$150.60
Purchase #2	$127.88	7.722%	$137.7549	$137.75	$137.75	$137.80
Purchase #3	$86.45	12.863%	$97.5701	$97.57	$97.55	$97.60
Purchase #4	$195.92	12.744%	$220.888	$220.89	$220.90	$220.90
Purchase #5	$27.80	13.317%	$31.5021	$31.50	$31.50	$31.50
Purchase #6	$192.35	4.352%	$200.7211	$200.72	$200.70	$200.70
Purchase #7	$39.98	7.135%	$42.8326	$42.83	$42.85	$42.80
7 purchase totals =	$812.12		$881.8846	$881.88	$881.85	$881.90