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	$81.81	5.376%	$86.2081	$86.21	$86.20	$86.20
Purchase #2	$238.73	7.184%	$255.8804	$255.88	$255.90	$255.90
Purchase #3	$234.86	8.679%	$255.2435	$255.24	$255.25	$255.20
Purchase #4	$10.60	11.512%	$11.8203	$11.82	$11.80	$11.80
Purchase #5	$40.74	9.404%	$44.5712	$44.57	$44.55	$44.60
Purchase #6	$31.60	8.505%	$34.2876	$34.29	$34.30	$34.30
Purchase #7	$90.95	5.157%	$95.6403	$95.64	$95.65	$95.60
7 purchase totals =	$729.29		$783.6514	$783.65	$783.65	$783.60