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	$169.38	10.621%	$187.3698	$187.37	$187.35	$187.40
Purchase #2	$40.41	13.614%	$45.9114	$45.91	$45.90	$45.90
Purchase #3	$24.37	12.517%	$27.4204	$27.42	$27.40	$27.40
Purchase #4	$38.73	13.747%	$44.0542	$44.05	$44.05	$44.10
Purchase #5	$44.29	9.183%	$48.3572	$48.36	$48.35	$48.40
Purchase #6	$168.88	4.183%	$175.9443	$175.94	$175.95	$175.90
Purchase #7	$247.65	13.431%	$280.9119	$280.91	$280.90	$280.90
7 purchase totals =	$733.71		$809.9692	$809.96	$809.90	$810.00