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	$213.79	8.191%	$231.3015	$231.30	$231.30	$231.30
Purchase #2	$74.47	7.700%	$80.2042	$80.20	$80.20	$80.20
Purchase #3	$230.45	6.768%	$246.0469	$246.05	$246.05	$246.00
Purchase #4	$230.72	12.455%	$259.4562	$259.46	$259.45	$259.50
Purchase #5	$56.95	12.418%	$64.0221	$64.02	$64.00	$64.00
Purchase #6	$96.59	4.202%	$100.6487	$100.65	$100.65	$100.60
Purchase #7	$94.83	5.378%	$99.93	$99.93	$99.95	$99.90
7 purchase totals =	$997.80		$1,081.6096	$1,081.61	$1,081.60	$1,081.50