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	$245.50	7.460%	$263.8143	$263.81	$263.80	$263.80
Purchase #2	$217.60	12.709%	$245.2548	$245.25	$245.25	$245.30
Purchase #3	$248.72	12.826%	$280.6208	$280.62	$280.60	$280.60
Purchase #4	$187.67	4.687%	$196.4661	$196.47	$196.45	$196.50
Purchase #5	$218.33	5.519%	$230.3796	$230.38	$230.40	$230.40
Purchase #6	$52.75	6.833%	$56.3544	$56.35	$56.35	$56.40
Purchase #7	$89.83	9.472%	$98.3387	$98.34	$98.35	$98.30
7 purchase totals =	$1,260.40		$1,371.2287	$1,371.22	$1,371.20	$1,371.30