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	$247.56	13.188%	$280.2082	$280.21	$280.20	$280.20
Purchase #2	$168.41	8.535%	$182.7838	$182.78	$182.80	$182.80
Purchase #3	$102.41	8.629%	$111.247	$111.25	$111.25	$111.20
Purchase #4	$214.50	3.484%	$221.9732	$221.97	$221.95	$222.00
Purchase #5	$147.81	12.521%	$166.3173	$166.32	$166.30	$166.30
Purchase #6	$169.41	10.404%	$187.0354	$187.04	$187.05	$187.00
Purchase #7	$192.88	10.139%	$212.4361	$212.44	$212.45	$212.40
7 purchase totals =	$1,242.98		$1,362.0010	$1,362.01	$1,362.00	$1,361.90