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	$224.87	11.523%	$250.7818	$250.78	$250.80	$250.80
Purchase #2	$100.94	6.164%	$107.1619	$107.16	$107.15	$107.20
Purchase #3	$36.60	13.282%	$41.4612	$41.46	$41.45	$41.50
Purchase #4	$242.76	5.194%	$255.369	$255.37	$255.35	$255.40
Purchase #5	$113.57	3.796%	$117.8811	$117.88	$117.90	$117.90
Purchase #6	$38.43	13.205%	$43.5047	$43.50	$43.50	$43.50
Purchase #7	$196.84	8.567%	$213.7033	$213.70	$213.70	$213.70
7 purchase totals =	$954.01		$1,029.8630	$1,029.85	$1,029.85	$1,030.00