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	$236.35	9.765%	$259.4296	$259.43	$259.45	$259.40
Purchase #2	$78.52	3.228%	$81.0546	$81.05	$81.05	$81.10
Purchase #3	$37.61	8.240%	$40.7091	$40.71	$40.70	$40.70
Purchase #4	$13.49	3.298%	$13.9349	$13.93	$13.95	$13.90
Purchase #5	$121.93	4.118%	$126.9511	$126.95	$126.95	$127.00
Purchase #6	$207.59	6.232%	$220.527	$220.53	$220.55	$220.50
Purchase #7	$73.78	12.373%	$82.9088	$82.91	$82.90	$82.90
7 purchase totals =	$769.27		$825.5151	$825.51	$825.55	$825.50