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	$194.42	12.679%	$219.0705	$219.07	$219.05	$219.10
Purchase #2	$39.85	3.392%	$41.2017	$41.20	$41.20	$41.20
Purchase #3	$119.30	12.221%	$133.8797	$133.88	$133.90	$133.90
Purchase #4	$225.71	7.409%	$242.4329	$242.43	$242.45	$242.40
Purchase #5	$194.91	8.505%	$211.4871	$211.49	$211.50	$211.50
Purchase #6	$123.86	7.870%	$133.6078	$133.61	$133.60	$133.60
Purchase #7	$83.93	6.667%	$89.5256	$89.53	$89.55	$89.50
7 purchase totals =	$981.98		$1,071.2053	$1,071.21	$1,071.25	$1,071.20