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	$173.34	10.477%	$191.5008	$191.50	$191.50	$191.50
Purchase #2	$73.52	5.358%	$77.4592	$77.46	$77.45	$77.50
Purchase #3	$78.37	9.269%	$85.6341	$85.63	$85.65	$85.60
Purchase #4	$24.52	10.218%	$27.0255	$27.03	$27.05	$27.00
Purchase #5	$71.58	12.423%	$80.4724	$80.47	$80.45	$80.50
Purchase #6	$188.98	10.264%	$208.3769	$208.38	$208.40	$208.40
Purchase #7	$248.49	5.233%	$261.4935	$261.49	$261.50	$261.50
7 purchase totals =	$858.80		$931.9624	$931.96	$932.00	$932.00