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	$110.72	3.192%	$114.2542	$114.25	$114.25	$114.30
Purchase #2	$201.84	11.824%	$225.7056	$225.71	$225.70	$225.70
Purchase #3	$70.39	11.756%	$78.665	$78.67	$78.65	$78.70
Purchase #4	$193.87	8.635%	$210.6107	$210.61	$210.60	$210.60
Purchase #5	$116.93	8.727%	$127.1345	$127.13	$127.15	$127.10
Purchase #6	$139.93	11.723%	$156.334	$156.33	$156.35	$156.30
Purchase #7	$118.34	10.689%	$130.9894	$130.99	$131.00	$131.00
7 purchase totals =	$952.02		$1,043.6934	$1,043.69	$1,043.70	$1,043.70