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	$118.95	10.665%	$131.636	$131.64	$131.65	$131.60
Purchase #2	$17.96	3.505%	$18.5895	$18.59	$18.60	$18.60
Purchase #3	$169.35	10.260%	$186.7253	$186.73	$186.75	$186.70
Purchase #4	$150.46	5.854%	$159.2679	$159.27	$159.25	$159.30
Purchase #5	$131.55	11.213%	$146.3007	$146.30	$146.30	$146.30
Purchase #6	$126.85	4.734%	$132.8551	$132.86	$132.85	$132.90
Purchase #7	$12.96	5.605%	$13.6864	$13.69	$13.70	$13.70
7 purchase totals =	$728.08		$789.0609	$789.08	$789.10	$789.10