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	$232.47	10.635%	$257.1932	$257.19	$257.20	$257.20
Purchase #2	$84.60	9.869%	$92.9492	$92.95	$92.95	$92.90
Purchase #3	$41.28	10.259%	$45.5149	$45.51	$45.50	$45.50
Purchase #4	$119.28	3.557%	$123.5228	$123.52	$123.50	$123.50
Purchase #5	$248.57	11.747%	$277.7695	$277.77	$277.75	$277.80
Purchase #6	$223.35	7.558%	$240.2308	$240.23	$240.25	$240.20
Purchase #7	$43.88	3.792%	$45.5439	$45.54	$45.55	$45.50
7 purchase totals =	$993.43		$1,082.7243	$1,082.71	$1,082.70	$1,082.60