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	$124.35	6.195%	$132.0535	$132.05	$132.05	$132.10
Purchase #2	$150.45	4.276%	$156.8832	$156.88	$156.90	$156.90
Purchase #3	$249.32	12.562%	$280.6396	$280.64	$280.65	$280.60
Purchase #4	$41.55	11.503%	$46.3295	$46.33	$46.35	$46.30
Purchase #5	$143.29	5.238%	$150.7955	$150.80	$150.80	$150.80
Purchase #6	$51.86	5.762%	$54.8482	$54.85	$54.85	$54.80
Purchase #7	$157.76	13.853%	$179.6145	$179.61	$179.60	$179.60
7 purchase totals =	$918.58		$1,001.1640	$1,001.16	$1,001.20	$1,001.10