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	$67.49	3.500%	$69.8522	$69.85	$69.85	$69.90
Purchase #2	$13.72	5.822%	$14.5188	$14.52	$14.50	$14.50
Purchase #3	$143.49	7.284%	$153.9418	$153.94	$153.95	$153.90
Purchase #4	$242.95	6.715%	$259.2641	$259.26	$259.25	$259.30
Purchase #5	$141.60	9.476%	$155.018	$155.02	$155.00	$155.00
Purchase #6	$29.91	12.145%	$33.5426	$33.54	$33.55	$33.50
Purchase #7	$41.93	3.746%	$43.5007	$43.50	$43.50	$43.50
7 purchase totals =	$681.09		$729.6382	$729.63	$729.60	$729.60