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	$35.68	13.340%	$40.4397	$40.44	$40.45	$40.40
Purchase #2	$63.46	3.667%	$65.7871	$65.79	$65.80	$65.80
Purchase #3	$150.72	6.124%	$159.9501	$159.95	$159.95	$160.00
Purchase #4	$174.59	7.130%	$187.0383	$187.04	$187.05	$187.00
Purchase #5	$116.68	13.453%	$132.377	$132.38	$132.40	$132.40
Purchase #6	$248.79	12.824%	$280.6948	$280.69	$280.70	$280.70
Purchase #7	$230.74	3.429%	$238.6521	$238.65	$238.65	$238.70
7 purchase totals =	$1,020.66		$1,104.9391	$1,104.94	$1,105.00	$1,105.00