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	$52.94	11.566%	$59.063	$59.06	$59.05	$59.10
Purchase #2	$108.57	4.701%	$113.6739	$113.67	$113.65	$113.70
Purchase #3	$39.29	9.691%	$43.0976	$43.10	$43.10	$43.10
Purchase #4	$48.98	7.480%	$52.6437	$52.64	$52.65	$52.60
Purchase #5	$71.44	3.432%	$73.8918	$73.89	$73.90	$73.90
Purchase #6	$29.37	7.820%	$31.6667	$31.67	$31.65	$31.70
Purchase #7	$171.32	12.612%	$192.9269	$192.93	$192.95	$192.90
7 purchase totals =	$521.91		$566.9636	$566.96	$566.95	$567.00