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	$43.29	6.379%	$46.0515	$46.05	$46.05	$46.10
Purchase #2	$156.83	3.797%	$162.7848	$162.78	$162.80	$162.80
Purchase #3	$16.82	9.619%	$18.4379	$18.44	$18.45	$18.40
Purchase #4	$100.70	10.872%	$111.6481	$111.65	$111.65	$111.60
Purchase #5	$250.43	12.155%	$280.8698	$280.87	$280.85	$280.90
Purchase #6	$144.47	8.224%	$156.3512	$156.35	$156.35	$156.40
Purchase #7	$230.96	6.186%	$245.2472	$245.25	$245.25	$245.20
7 purchase totals =	$943.50		$1,021.3905	$1,021.39	$1,021.40	$1,021.40