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	$238.57	13.208%	$270.0803	$270.08	$270.10	$270.10
Purchase #2	$19.37	4.864%	$20.3122	$20.31	$20.30	$20.30
Purchase #3	$170.60	4.277%	$177.8966	$177.90	$177.90	$177.90
Purchase #4	$65.78	4.345%	$68.6381	$68.64	$68.65	$68.60
Purchase #5	$224.32	6.266%	$238.3759	$238.38	$238.40	$238.40
Purchase #6	$144.46	5.529%	$152.4472	$152.45	$152.45	$152.40
Purchase #7	$80.77	13.451%	$91.6344	$91.63	$91.65	$91.60
7 purchase totals =	$943.87		$1,019.3847	$1,019.39	$1,019.45	$1,019.30