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	$126.33	12.607%	$142.2564	$142.26	$142.25	$142.30
Purchase #2	$245.56	6.680%	$261.9634	$261.96	$261.95	$262.00
Purchase #3	$136.41	3.430%	$141.0889	$141.09	$141.10	$141.10
Purchase #4	$29.98	11.470%	$33.4187	$33.42	$33.40	$33.40
Purchase #5	$65.39	5.352%	$68.8897	$68.89	$68.90	$68.90
Purchase #6	$211.44	4.802%	$221.5933	$221.59	$221.60	$221.60
Purchase #7	$52.70	13.193%	$59.6527	$59.65	$59.65	$59.70
7 purchase totals =	$867.81		$928.8631	$928.86	$928.85	$929.00