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	$46.92	10.430%	$51.8138	$51.81	$51.80	$51.80
Purchase #2	$105.30	13.153%	$119.1501	$119.15	$119.15	$119.20
Purchase #3	$35.34	11.632%	$39.4507	$39.45	$39.45	$39.50
Purchase #4	$186.91	5.167%	$196.5676	$196.57	$196.55	$196.60
Purchase #5	$201.72	3.660%	$209.103	$209.10	$209.10	$209.10
Purchase #6	$43.44	4.626%	$45.4495	$45.45	$45.45	$45.40
Purchase #7	$88.89	9.423%	$97.2661	$97.27	$97.25	$97.30
7 purchase totals =	$708.52		$758.8008	$758.80	$758.75	$758.90