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	$107.91	13.377%	$122.3451	$122.35	$122.35	$122.30
Purchase #2	$73.34	7.536%	$78.8669	$78.87	$78.85	$78.90
Purchase #3	$65.26	9.870%	$71.7012	$71.70	$71.70	$71.70
Purchase #4	$40.49	7.419%	$43.494	$43.49	$43.50	$43.50
Purchase #5	$238.38	6.364%	$253.5505	$253.55	$253.55	$253.60
Purchase #6	$250.83	9.742%	$275.2659	$275.27	$275.25	$275.30
Purchase #7	$219.95	4.863%	$230.6462	$230.65	$230.65	$230.60
7 purchase totals =	$996.16		$1,075.8698	$1,075.88	$1,075.85	$1,075.90