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	$234.60	12.490%	$263.9015	$263.90	$263.90	$263.90
Purchase #2	$175.68	11.561%	$195.9904	$195.99	$196.00	$196.00
Purchase #3	$244.38	10.658%	$270.426	$270.43	$270.45	$270.40
Purchase #4	$164.75	9.166%	$179.851	$179.85	$179.85	$179.90
Purchase #5	$206.54	5.242%	$217.3668	$217.37	$217.35	$217.40
Purchase #6	$33.69	11.138%	$37.4424	$37.44	$37.45	$37.40
Purchase #7	$183.25	7.279%	$196.5888	$196.59	$196.60	$196.60
7 purchase totals =	$1,242.89		$1,361.5669	$1,361.57	$1,361.60	$1,361.60