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	$208.95	8.377%	$226.4537	$226.45	$226.45	$226.50
Purchase #2	$89.27	10.393%	$98.5478	$98.55	$98.55	$98.50
Purchase #3	$20.57	3.384%	$21.2661	$21.27	$21.25	$21.30
Purchase #4	$73.86	13.119%	$83.5497	$83.55	$83.55	$83.50
Purchase #5	$234.70	4.738%	$245.8201	$245.82	$245.80	$245.80
Purchase #6	$30.54	11.664%	$34.1022	$34.10	$34.10	$34.10
Purchase #7	$142.38	9.263%	$155.5687	$155.57	$155.55	$155.60
7 purchase totals =	$800.27		$865.3083	$865.31	$865.25	$865.30