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	$190.79	5.696%	$201.6574	$201.66	$201.65	$201.70
Purchase #2	$98.97	12.578%	$111.4184	$111.42	$111.40	$111.40
Purchase #3	$103.32	11.782%	$115.4932	$115.49	$115.50	$115.50
Purchase #4	$139.67	13.546%	$158.5897	$158.59	$158.60	$158.60
Purchase #5	$54.42	9.240%	$59.4484	$59.45	$59.45	$59.40
Purchase #6	$34.53	13.271%	$39.1125	$39.11	$39.10	$39.10
Purchase #7	$31.96	4.767%	$33.4835	$33.48	$33.50	$33.50
7 purchase totals =	$653.66		$719.2031	$719.20	$719.20	$719.20