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	$125.59	6.455%	$133.6968	$133.70	$133.70	$133.70
Purchase #2	$22.51	11.127%	$25.0147	$25.01	$25.00	$25.00
Purchase #3	$136.44	10.669%	$150.9968	$151.00	$151.00	$151.00
Purchase #4	$112.90	9.103%	$123.1773	$123.18	$123.20	$123.20
Purchase #5	$75.88	3.239%	$78.3378	$78.34	$78.35	$78.30
Purchase #6	$165.38	9.499%	$181.0894	$181.09	$181.10	$181.10
Purchase #7	$114.79	7.444%	$123.335	$123.34	$123.35	$123.30
7 purchase totals =	$753.49		$815.6478	$815.66	$815.70	$815.60