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	$53.40	11.128%	$59.3424	$59.34	$59.35	$59.30
Purchase #2	$212.57	4.225%	$221.5511	$221.55	$221.55	$221.60
Purchase #3	$81.96	7.721%	$88.2881	$88.29	$88.30	$88.30
Purchase #4	$234.57	7.299%	$251.6913	$251.69	$251.70	$251.70
Purchase #5	$104.82	8.129%	$113.3408	$113.34	$113.35	$113.30
Purchase #6	$208.47	5.235%	$219.3834	$219.38	$219.40	$219.40
Purchase #7	$50.27	9.217%	$54.9034	$54.90	$54.90	$54.90
7 purchase totals =	$946.06		$1,008.5005	$1,008.49	$1,008.55	$1,008.50