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	$9.54	5.849%	$10.098	$10.10	$10.10	$10.10
Purchase #2	$228.38	12.114%	$256.046	$256.05	$256.05	$256.00
Purchase #3	$245.43	4.505%	$256.4866	$256.49	$256.50	$256.50
Purchase #4	$201.39	4.716%	$210.8876	$210.89	$210.90	$210.90
Purchase #5	$134.67	13.523%	$152.8814	$152.88	$152.90	$152.90
Purchase #6	$208.86	8.375%	$226.352	$226.35	$226.35	$226.40
Purchase #7	$105.91	8.372%	$114.7768	$114.78	$114.80	$114.80
7 purchase totals =	$1,134.18		$1,227.5284	$1,227.54	$1,227.60	$1,227.60