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	$202.68	5.824%	$214.4841	$214.48	$214.50	$214.50
Purchase #2	$126.66	6.479%	$134.8663	$134.87	$134.85	$134.90
Purchase #3	$18.65	12.830%	$21.0428	$21.04	$21.05	$21.00
Purchase #4	$59.47	10.342%	$65.6204	$65.62	$65.60	$65.60
Purchase #5	$205.43	6.270%	$218.3105	$218.31	$218.30	$218.30
Purchase #6	$246.48	13.856%	$280.6323	$280.63	$280.65	$280.60
Purchase #7	$114.26	12.447%	$128.4819	$128.48	$128.50	$128.50
7 purchase totals =	$973.63		$1,063.4383	$1,063.43	$1,063.45	$1,063.40