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	$48.48	8.570%	$52.6347	$52.63	$52.65	$52.60
Purchase #2	$124.61	12.724%	$140.4654	$140.47	$140.45	$140.50
Purchase #3	$119.79	11.384%	$133.4269	$133.43	$133.45	$133.40
Purchase #4	$202.87	11.277%	$225.7476	$225.75	$225.75	$225.70
Purchase #5	$20.61	4.682%	$21.575	$21.58	$21.60	$21.60
Purchase #6	$73.51	6.520%	$78.3029	$78.30	$78.30	$78.30
Purchase #7	$98.72	7.799%	$106.4192	$106.42	$106.40	$106.40
7 purchase totals =	$688.59		$758.5717	$758.58	$758.60	$758.50