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	$114.43	8.535%	$124.1966	$124.20	$124.20	$124.20
Purchase #2	$194.30	8.856%	$211.5072	$211.51	$211.50	$211.50
Purchase #3	$168.29	11.484%	$187.6164	$187.62	$187.60	$187.60
Purchase #4	$145.86	7.587%	$156.9264	$156.93	$156.95	$156.90
Purchase #5	$101.65	7.238%	$109.0074	$109.01	$109.00	$109.00
Purchase #6	$153.37	3.324%	$158.468	$158.47	$158.45	$158.50
Purchase #7	$57.93	5.563%	$61.1526	$61.15	$61.15	$61.20
7 purchase totals =	$935.83		$1,008.8746	$1,008.89	$1,008.85	$1,008.90