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	$156.71	5.213%	$164.8793	$164.88	$164.90	$164.90
Purchase #2	$44.25	4.688%	$46.3244	$46.32	$46.30	$46.30
Purchase #3	$71.78	8.522%	$77.8971	$77.90	$77.90	$77.90
Purchase #4	$117.62	12.487%	$132.3072	$132.31	$132.30	$132.30
Purchase #5	$73.45	5.113%	$77.2055	$77.21	$77.20	$77.20
Purchase #6	$84.31	9.603%	$92.4063	$92.41	$92.40	$92.40
Purchase #7	$17.61	4.591%	$18.4185	$18.42	$18.40	$18.40
7 purchase totals =	$565.73		$609.4383	$609.45	$609.40	$609.40