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	$156.44	9.600%	$171.4582	$171.46	$171.45	$171.50
Purchase #2	$120.87	13.799%	$137.5489	$137.55	$137.55	$137.50
Purchase #3	$199.81	9.343%	$218.4782	$218.48	$218.50	$218.50
Purchase #4	$181.83	6.502%	$193.6526	$193.65	$193.65	$193.70
Purchase #5	$112.78	12.619%	$127.0117	$127.01	$127.00	$127.00
Purchase #6	$74.33	6.210%	$78.9459	$78.95	$78.95	$78.90
Purchase #7	$122.96	4.786%	$128.8449	$128.84	$128.85	$128.80
7 purchase totals =	$969.02		$1,055.9404	$1,055.94	$1,055.95	$1,055.90