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	$51.73	7.182%	$55.4452	$55.45	$55.45	$55.40
Purchase #2	$172.87	13.588%	$196.3596	$196.36	$196.35	$196.40
Purchase #3	$90.25	12.868%	$101.8634	$101.86	$101.85	$101.90
Purchase #4	$115.91	12.595%	$130.5089	$130.51	$130.50	$130.50
Purchase #5	$241.69	7.375%	$259.5146	$259.51	$259.50	$259.50
Purchase #6	$186.62	11.772%	$208.5889	$208.59	$208.60	$208.60
Purchase #7	$197.68	10.113%	$217.6714	$217.67	$217.65	$217.70
7 purchase totals =	$1,056.75		$1,169.9520	$1,169.95	$1,169.90	$1,170.00