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	$181.50	12.338%	$203.8935	$203.89	$203.90	$203.90
Purchase #2	$76.43	10.510%	$84.4628	$84.46	$84.45	$84.50
Purchase #3	$106.41	5.141%	$111.8805	$111.88	$111.90	$111.90
Purchase #4	$43.97	6.760%	$46.9424	$46.94	$46.95	$46.90
Purchase #5	$93.78	6.156%	$99.5531	$99.55	$99.55	$99.60
Purchase #6	$48.80	13.126%	$55.2055	$55.21	$55.20	$55.20
Purchase #7	$149.89	9.707%	$164.4398	$164.44	$164.45	$164.40
7 purchase totals =	$700.78		$766.3776	$766.37	$766.40	$766.40