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	$105.84	6.633%	$112.8604	$112.86	$112.85	$112.90
Purchase #2	$200.90	7.227%	$215.419	$215.42	$215.40	$215.40
Purchase #3	$81.74	4.643%	$85.5352	$85.54	$85.55	$85.50
Purchase #4	$161.81	12.192%	$181.5379	$181.54	$181.55	$181.50
Purchase #5	$81.34	7.358%	$87.325	$87.33	$87.35	$87.30
Purchase #6	$238.92	5.268%	$251.5063	$251.51	$251.50	$251.50
Purchase #7	$120.69	10.771%	$133.6895	$133.69	$133.70	$133.70
7 purchase totals =	$991.24		$1,067.8733	$1,067.89	$1,067.90	$1,067.80