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	$231.69	9.329%	$253.3044	$253.30	$253.30	$253.30
Purchase #2	$238.43	7.527%	$256.3766	$256.38	$256.40	$256.40
Purchase #3	$12.60	9.843%	$13.8402	$13.84	$13.85	$13.80
Purchase #4	$40.69	3.854%	$42.2582	$42.26	$42.25	$42.30
Purchase #5	$201.97	3.675%	$209.3924	$209.39	$209.40	$209.40
Purchase #6	$37.81	4.579%	$39.5413	$39.54	$39.55	$39.50
Purchase #7	$46.82	12.218%	$52.5405	$52.54	$52.55	$52.50
7 purchase totals =	$810.01		$867.2536	$867.25	$867.30	$867.20