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	$202.98	13.161%	$229.6942	$229.69	$229.70	$229.70
Purchase #2	$177.61	10.645%	$196.5166	$196.52	$196.50	$196.50
Purchase #3	$167.65	7.672%	$180.5121	$180.51	$180.50	$180.50
Purchase #4	$56.49	10.809%	$62.596	$62.60	$62.60	$62.60
Purchase #5	$135.92	9.207%	$148.4342	$148.43	$148.45	$148.40
Purchase #6	$104.32	10.114%	$114.8709	$114.87	$114.85	$114.90
Purchase #7	$100.96	10.207%	$111.265	$111.27	$111.25	$111.30
7 purchase totals =	$945.93		$1,043.8890	$1,043.89	$1,043.85	$1,043.90