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	$126.45	13.587%	$143.6308	$143.63	$143.65	$143.60
Purchase #2	$148.41	6.544%	$158.122	$158.12	$158.10	$158.10
Purchase #3	$24.36	11.800%	$27.2345	$27.23	$27.25	$27.20
Purchase #4	$78.44	8.415%	$85.0407	$85.04	$85.05	$85.00
Purchase #5	$105.69	5.397%	$111.3941	$111.39	$111.40	$111.40
Purchase #6	$240.37	9.418%	$263.008	$263.01	$263.00	$263.00
Purchase #7	$31.63	6.392%	$33.6518	$33.65	$33.65	$33.70
7 purchase totals =	$755.35		$822.0819	$822.07	$822.10	$822.00