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	$95.81	13.723%	$108.958	$108.96	$108.95	$109.00
Purchase #2	$42.58	11.161%	$47.3324	$47.33	$47.35	$47.30
Purchase #3	$118.29	4.118%	$123.1612	$123.16	$123.15	$123.20
Purchase #4	$132.71	7.193%	$142.2558	$142.26	$142.25	$142.30
Purchase #5	$38.51	12.774%	$43.4293	$43.43	$43.45	$43.40
Purchase #6	$143.25	9.360%	$156.6582	$156.66	$156.65	$156.70
Purchase #7	$161.59	6.214%	$171.6312	$171.63	$171.65	$171.60
7 purchase totals =	$732.74		$793.4261	$793.43	$793.45	$793.50