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	$151.83	10.317%	$167.4943	$167.49	$167.50	$167.50
Purchase #2	$19.91	3.640%	$20.6347	$20.63	$20.65	$20.60
Purchase #3	$49.51	4.808%	$51.8904	$51.89	$51.90	$51.90
Purchase #4	$39.78	10.422%	$43.9259	$43.93	$43.95	$43.90
Purchase #5	$34.47	6.265%	$36.6295	$36.63	$36.65	$36.60
Purchase #6	$139.45	11.410%	$155.3612	$155.36	$155.35	$155.40
Purchase #7	$159.98	12.841%	$180.523	$180.52	$180.50	$180.50
7 purchase totals =	$594.93		$656.4590	$656.45	$656.50	$656.40