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	$226.52	3.332%	$234.0676	$234.07	$234.05	$234.10
Purchase #2	$220.68	5.659%	$233.1683	$233.17	$233.15	$233.20
Purchase #3	$38.67	5.542%	$40.8131	$40.81	$40.80	$40.80
Purchase #4	$57.54	3.395%	$59.4935	$59.49	$59.50	$59.50
Purchase #5	$234.27	6.124%	$248.6167	$248.62	$248.60	$248.60
Purchase #6	$179.64	13.294%	$203.5213	$203.52	$203.50	$203.50
Purchase #7	$62.65	7.442%	$67.3124	$67.31	$67.30	$67.30
7 purchase totals =	$1,019.97		$1,086.9929	$1,086.99	$1,086.90	$1,087.00