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	$235.47	9.195%	$257.1215	$257.12	$257.10	$257.10
Purchase #2	$169.66	5.695%	$179.3221	$179.32	$179.30	$179.30
Purchase #3	$38.63	13.425%	$43.8161	$43.82	$43.80	$43.80
Purchase #4	$103.71	7.602%	$111.594	$111.59	$111.60	$111.60
Purchase #5	$115.71	10.480%	$127.8364	$127.84	$127.85	$127.80
Purchase #6	$195.92	8.853%	$213.2648	$213.26	$213.25	$213.30
Purchase #7	$114.90	9.500%	$125.8155	$125.82	$125.80	$125.80
7 purchase totals =	$974.00		$1,058.7704	$1,058.77	$1,058.70	$1,058.70