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	$119.37	12.196%	$133.9284	$133.93	$133.95	$133.90
Purchase #2	$39.76	12.688%	$44.8047	$44.80	$44.80	$44.80
Purchase #3	$166.32	6.291%	$176.7832	$176.78	$176.80	$176.80
Purchase #4	$38.32	13.326%	$43.4265	$43.43	$43.45	$43.40
Purchase #5	$191.87	6.269%	$203.8983	$203.90	$203.90	$203.90
Purchase #6	$81.89	10.210%	$90.251	$90.25	$90.25	$90.30
Purchase #7	$35.49	7.746%	$38.2391	$38.24	$38.25	$38.20
7 purchase totals =	$673.02		$731.3312	$731.33	$731.40	$731.30