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	$35.82	6.341%	$38.0913	$38.09	$38.10	$38.10
Purchase #2	$86.71	3.588%	$89.8212	$89.82	$89.80	$89.80
Purchase #3	$39.50	3.628%	$40.9331	$40.93	$40.95	$40.90
Purchase #4	$32.98	9.164%	$36.0023	$36.00	$36.00	$36.00
Purchase #5	$10.70	12.598%	$12.048	$12.05	$12.05	$12.00
Purchase #6	$132.67	5.855%	$140.4378	$140.44	$140.45	$140.40
Purchase #7	$231.51	5.350%	$243.8958	$243.90	$243.90	$243.90
7 purchase totals =	$569.89		$601.2295	$601.23	$601.25	$601.10