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	$212.27	13.788%	$241.5378	$241.54	$241.55	$241.50
Purchase #2	$156.32	8.339%	$169.3555	$169.36	$169.35	$169.40
Purchase #3	$18.62	3.391%	$19.2514	$19.25	$19.25	$19.30
Purchase #4	$32.45	13.769%	$36.918	$36.92	$36.90	$36.90
Purchase #5	$116.60	9.423%	$127.5872	$127.59	$127.60	$127.60
Purchase #6	$172.46	11.281%	$191.9152	$191.92	$191.90	$191.90
Purchase #7	$199.79	3.418%	$206.6188	$206.62	$206.60	$206.60
7 purchase totals =	$908.51		$993.1839	$993.20	$993.15	$993.20