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	$113.53	9.746%	$124.5946	$124.59	$124.60	$124.60
Purchase #2	$108.98	12.872%	$123.0079	$123.01	$123.00	$123.00
Purchase #3	$202.49	5.195%	$213.0094	$213.01	$213.00	$213.00
Purchase #4	$157.56	10.576%	$174.2235	$174.22	$174.20	$174.20
Purchase #5	$161.91	6.571%	$172.5491	$172.55	$172.55	$172.50
Purchase #6	$126.41	3.273%	$130.5474	$130.55	$130.55	$130.50
Purchase #7	$128.42	12.590%	$144.5881	$144.59	$144.60	$144.60
7 purchase totals =	$999.30		$1,082.5200	$1,082.52	$1,082.50	$1,082.40