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	$217.78	10.854%	$241.4178	$241.42	$241.40	$241.40
Purchase #2	$7.33	7.401%	$7.8725	$7.87	$7.85	$7.90
Purchase #3	$189.33	12.713%	$213.3995	$213.40	$213.40	$213.40
Purchase #4	$186.89	11.797%	$208.9374	$208.94	$208.95	$208.90
Purchase #5	$73.89	6.343%	$78.5768	$78.58	$78.60	$78.60
Purchase #6	$125.28	12.127%	$140.4727	$140.47	$140.45	$140.50
Purchase #7	$15.28	10.512%	$16.8862	$16.89	$16.90	$16.90
7 purchase totals =	$815.78		$907.5629	$907.57	$907.55	$907.60