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	$41.54	4.372%	$43.3561	$43.36	$43.35	$43.40
Purchase #2	$155.70	13.415%	$176.5872	$176.59	$176.60	$176.60
Purchase #3	$214.71	13.393%	$243.4661	$243.47	$243.45	$243.50
Purchase #4	$40.83	6.722%	$43.5746	$43.57	$43.55	$43.60
Purchase #5	$132.88	6.381%	$141.3591	$141.36	$141.35	$141.40
Purchase #6	$105.70	6.817%	$112.9056	$112.91	$112.90	$112.90
Purchase #7	$230.59	12.562%	$259.5567	$259.56	$259.55	$259.60
7 purchase totals =	$921.95		$1,020.8054	$1,020.82	$1,020.75	$1,021.00