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	$130.88	9.510%	$143.3267	$143.33	$143.35	$143.30
Purchase #2	$231.86	4.137%	$241.452	$241.45	$241.45	$241.50
Purchase #3	$135.90	6.712%	$145.0216	$145.02	$145.00	$145.00
Purchase #4	$66.53	7.624%	$71.6022	$71.60	$71.60	$71.60
Purchase #5	$104.89	12.464%	$117.9635	$117.96	$117.95	$118.00
Purchase #6	$88.79	13.639%	$100.9001	$100.90	$100.90	$100.90
Purchase #7	$78.51	5.775%	$83.044	$83.04	$83.05	$83.00
7 purchase totals =	$837.36		$903.3101	$903.30	$903.30	$903.30