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	$55.33	13.120%	$62.5893	$62.59	$62.60	$62.60
Purchase #2	$248.66	6.704%	$265.3302	$265.33	$265.35	$265.30
Purchase #3	$38.53	13.818%	$43.8541	$43.85	$43.85	$43.90
Purchase #4	$155.89	10.124%	$171.6723	$171.67	$171.65	$171.70
Purchase #5	$67.54	13.166%	$76.4323	$76.43	$76.45	$76.40
Purchase #6	$121.43	12.856%	$137.041	$137.04	$137.05	$137.00
Purchase #7	$112.38	8.477%	$121.9065	$121.91	$121.90	$121.90
7 purchase totals =	$799.76		$878.8257	$878.82	$878.85	$878.80