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	$130.31	5.636%	$137.6543	$137.65	$137.65	$137.70
Purchase #2	$35.87	9.259%	$39.1912	$39.19	$39.20	$39.20
Purchase #3	$113.64	4.297%	$118.5231	$118.52	$118.50	$118.50
Purchase #4	$14.93	10.739%	$16.5333	$16.53	$16.55	$16.50
Purchase #5	$90.33	10.231%	$99.5717	$99.57	$99.55	$99.60
Purchase #6	$105.36	11.866%	$117.862	$117.86	$117.85	$117.90
Purchase #7	$109.69	12.204%	$123.0766	$123.08	$123.10	$123.10
7 purchase totals =	$600.13		$652.4122	$652.40	$652.40	$652.50