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	$133.25	9.443%	$145.8328	$145.83	$145.85	$145.80
Purchase #2	$101.59	7.164%	$108.8679	$108.87	$108.85	$108.90
Purchase #3	$43.42	3.510%	$44.944	$44.94	$44.95	$44.90
Purchase #4	$218.31	3.478%	$225.9028	$225.90	$225.90	$225.90
Purchase #5	$200.69	8.538%	$217.8249	$217.82	$217.80	$217.80
Purchase #6	$140.55	10.800%	$155.7294	$155.73	$155.75	$155.70
Purchase #7	$174.64	12.760%	$196.9241	$196.92	$196.90	$196.90
7 purchase totals =	$1,012.45		$1,096.0259	$1,096.01	$1,096.00	$1,095.90