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	$155.35	11.422%	$173.0941	$173.09	$173.10	$173.10
Purchase #2	$246.31	13.803%	$280.3082	$280.31	$280.30	$280.30
Purchase #3	$67.82	12.725%	$76.4501	$76.45	$76.45	$76.50
Purchase #4	$65.64	9.404%	$71.8128	$71.81	$71.80	$71.80
Purchase #5	$112.47	11.596%	$125.512	$125.51	$125.50	$125.50
Purchase #6	$238.25	12.418%	$267.8359	$267.84	$267.85	$267.80
Purchase #7	$84.93	6.621%	$90.5532	$90.55	$90.55	$90.60
7 purchase totals =	$970.77		$1,085.5663	$1,085.56	$1,085.55	$1,085.60