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	$229.30	3.295%	$236.8554	$236.86	$236.85	$236.90
Purchase #2	$233.55	7.555%	$251.1947	$251.19	$251.20	$251.20
Purchase #3	$230.29	11.238%	$256.17	$256.17	$256.15	$256.20
Purchase #4	$52.63	4.284%	$54.8847	$54.88	$54.90	$54.90
Purchase #5	$108.41	12.372%	$121.8225	$121.82	$121.80	$121.80
Purchase #6	$40.38	12.492%	$45.4243	$45.42	$45.40	$45.40
Purchase #7	$123.54	12.517%	$139.0035	$139.00	$139.00	$139.00
7 purchase totals =	$1,018.10		$1,105.3551	$1,105.34	$1,105.30	$1,105.40