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	$233.61	13.470%	$265.0773	$265.08	$265.10	$265.10
Purchase #2	$250.32	9.536%	$274.1905	$274.19	$274.20	$274.20
Purchase #3	$45.80	3.815%	$47.5473	$47.55	$47.55	$47.50
Purchase #4	$103.94	13.663%	$118.1413	$118.14	$118.15	$118.10
Purchase #5	$178.60	6.842%	$190.8198	$190.82	$190.80	$190.80
Purchase #6	$43.53	6.807%	$46.4931	$46.49	$46.50	$46.50
Purchase #7	$92.43	9.639%	$101.3393	$101.34	$101.35	$101.30
7 purchase totals =	$948.23		$1,043.6086	$1,043.61	$1,043.65	$1,043.50