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	$118.25	12.297%	$132.7912	$132.79	$132.80	$132.80
Purchase #2	$80.63	8.465%	$87.4553	$87.46	$87.45	$87.50
Purchase #3	$105.83	8.839%	$115.1843	$115.18	$115.20	$115.20
Purchase #4	$65.73	8.618%	$71.3946	$71.39	$71.40	$71.40
Purchase #5	$203.75	7.105%	$218.2264	$218.23	$218.25	$218.20
Purchase #6	$61.43	8.172%	$66.4501	$66.45	$66.45	$66.50
Purchase #7	$116.95	8.871%	$127.3246	$127.32	$127.30	$127.30
7 purchase totals =	$752.57		$818.8265	$818.82	$818.85	$818.90