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	$140.47	7.429%	$150.9055	$150.91	$150.90	$150.90
Purchase #2	$59.43	6.402%	$63.2347	$63.23	$63.25	$63.20
Purchase #3	$213.65	7.174%	$228.9773	$228.98	$229.00	$229.00
Purchase #4	$198.61	8.543%	$215.5773	$215.58	$215.60	$215.60
Purchase #5	$196.30	13.758%	$223.307	$223.31	$223.30	$223.30
Purchase #6	$177.80	5.257%	$187.1469	$187.15	$187.15	$187.10
Purchase #7	$9.88	13.300%	$11.194	$11.19	$11.20	$11.20
7 purchase totals =	$996.14		$1,080.3427	$1,080.35	$1,080.40	$1,080.30