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	$18.73	3.447%	$19.3756	$19.38	$19.40	$19.40
Purchase #2	$64.35	11.652%	$71.8481	$71.85	$71.85	$71.80
Purchase #3	$57.32	10.775%	$63.4962	$63.50	$63.50	$63.50
Purchase #4	$196.56	10.628%	$217.4504	$217.45	$217.45	$217.50
Purchase #5	$182.69	7.443%	$196.2876	$196.29	$196.30	$196.30
Purchase #6	$151.50	4.193%	$157.8524	$157.85	$157.85	$157.90
Purchase #7	$54.54	3.656%	$56.534	$56.53	$56.55	$56.50
7 purchase totals =	$725.69		$782.8443	$782.85	$782.90	$782.90