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	$247.65	12.834%	$279.4334	$279.43	$279.45	$279.40
Purchase #2	$37.47	9.128%	$40.8903	$40.89	$40.90	$40.90
Purchase #3	$40.32	8.518%	$43.7545	$43.75	$43.75	$43.80
Purchase #4	$120.53	3.235%	$124.4291	$124.43	$124.45	$124.40
Purchase #5	$137.69	11.822%	$153.9677	$153.97	$153.95	$154.00
Purchase #6	$149.49	4.755%	$156.5982	$156.60	$156.60	$156.60
Purchase #7	$216.84	13.185%	$245.4304	$245.43	$245.45	$245.40
7 purchase totals =	$949.99		$1,044.5036	$1,044.50	$1,044.55	$1,044.50