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	$132.63	6.393%	$141.109	$141.11	$141.10	$141.10
Purchase #2	$114.38	10.372%	$126.2435	$126.24	$126.25	$126.20
Purchase #3	$42.88	11.841%	$47.9574	$47.96	$47.95	$48.00
Purchase #4	$243.27	11.238%	$270.6087	$270.61	$270.60	$270.60
Purchase #5	$140.78	7.244%	$150.9781	$150.98	$151.00	$151.00
Purchase #6	$133.87	4.393%	$139.7509	$139.75	$139.75	$139.80
Purchase #7	$51.95	13.645%	$59.0386	$59.04	$59.05	$59.00
7 purchase totals =	$859.76		$935.6862	$935.69	$935.70	$935.70