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	$181.93	8.184%	$196.8192	$196.82	$196.80	$196.80
Purchase #2	$126.57	3.612%	$131.1417	$131.14	$131.15	$131.10
Purchase #3	$6.59	8.724%	$7.1649	$7.16	$7.15	$7.20
Purchase #4	$217.40	4.164%	$226.4525	$226.45	$226.45	$226.50
Purchase #5	$143.27	10.199%	$157.8821	$157.88	$157.90	$157.90
Purchase #6	$43.48	3.549%	$45.0231	$45.02	$45.00	$45.00
Purchase #7	$123.49	9.670%	$135.4315	$135.43	$135.45	$135.40
7 purchase totals =	$842.73		$899.9150	$899.90	$899.90	$899.90