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	$215.59	3.406%	$222.933	$222.93	$222.95	$222.90
Purchase #2	$190.91	10.724%	$211.3832	$211.38	$211.40	$211.40
Purchase #3	$192.36	12.702%	$216.7936	$216.79	$216.80	$216.80
Purchase #4	$30.72	3.735%	$31.8674	$31.87	$31.85	$31.90
Purchase #5	$133.48	6.548%	$142.2203	$142.22	$142.20	$142.20
Purchase #6	$59.27	12.789%	$66.85	$66.85	$66.85	$66.90
Purchase #7	$164.69	8.753%	$179.1053	$179.11	$179.10	$179.10
7 purchase totals =	$987.02		$1,071.1528	$1,071.15	$1,071.15	$1,071.20