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	$6.29	12.830%	$7.097	$7.10	$7.10	$7.10
Purchase #2	$214.43	3.307%	$221.5212	$221.52	$221.50	$221.50
Purchase #3	$58.86	6.482%	$62.6753	$62.68	$62.70	$62.70
Purchase #4	$232.94	7.447%	$250.287	$250.29	$250.30	$250.30
Purchase #5	$61.40	3.491%	$63.5435	$63.54	$63.55	$63.50
Purchase #6	$221.60	5.300%	$233.3448	$233.34	$233.35	$233.30
Purchase #7	$101.86	9.323%	$111.3564	$111.36	$111.35	$111.40
7 purchase totals =	$897.38		$949.8252	$949.83	$949.85	$949.80