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	$238.46	7.200%	$255.6291	$255.63	$255.65	$255.60
Purchase #2	$219.32	9.843%	$240.9077	$240.91	$240.90	$240.90
Purchase #3	$119.87	13.771%	$136.3773	$136.38	$136.40	$136.40
Purchase #4	$174.59	13.478%	$198.1212	$198.12	$198.10	$198.10
Purchase #5	$115.83	13.615%	$131.6003	$131.60	$131.60	$131.60
Purchase #6	$118.88	13.845%	$135.3389	$135.34	$135.35	$135.30
Purchase #7	$180.68	8.575%	$196.1733	$196.17	$196.15	$196.20
7 purchase totals =	$1,167.63		$1,294.1478	$1,294.15	$1,294.15	$1,294.10