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	$117.70	13.676%	$133.7967	$133.80	$133.80	$133.80
Purchase #2	$217.43	9.327%	$237.7097	$237.71	$237.70	$237.70
Purchase #3	$98.76	12.439%	$111.0448	$111.04	$111.05	$111.00
Purchase #4	$181.67	8.230%	$196.6214	$196.62	$196.60	$196.60
Purchase #5	$120.52	8.822%	$131.1523	$131.15	$131.15	$131.20
Purchase #6	$148.78	9.431%	$162.8114	$162.81	$162.80	$162.80
Purchase #7	$123.87	3.738%	$128.5003	$128.50	$128.50	$128.50
7 purchase totals =	$1,008.73		$1,101.6366	$1,101.63	$1,101.60	$1,101.60