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	$235.84	5.264%	$248.2546	$248.25	$248.25	$248.30
Purchase #2	$197.48	12.452%	$222.0702	$222.07	$222.05	$222.10
Purchase #3	$85.44	4.800%	$89.5411	$89.54	$89.55	$89.50
Purchase #4	$34.62	3.568%	$35.8552	$35.86	$35.85	$35.90
Purchase #5	$226.88	4.556%	$237.2167	$237.22	$237.20	$237.20
Purchase #6	$44.38	10.166%	$48.8917	$48.89	$48.90	$48.90
Purchase #7	$172.81	8.724%	$187.8859	$187.89	$187.90	$187.90
7 purchase totals =	$997.45		$1,069.7154	$1,069.72	$1,069.70	$1,069.80