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	$131.25	6.695%	$140.0372	$140.04	$140.05	$140.00
Purchase #2	$124.63	6.124%	$132.2623	$132.26	$132.25	$132.30
Purchase #3	$59.62	3.388%	$61.6399	$61.64	$61.65	$61.60
Purchase #4	$75.85	12.371%	$85.2334	$85.23	$85.25	$85.20
Purchase #5	$185.90	5.548%	$196.2137	$196.21	$196.20	$196.20
Purchase #6	$47.54	13.326%	$53.8752	$53.88	$53.90	$53.90
Purchase #7	$27.46	8.493%	$29.7922	$29.79	$29.80	$29.80
7 purchase totals =	$652.25		$699.0539	$699.05	$699.10	$699.00