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	$242.33	10.843%	$268.6058	$268.61	$268.60	$268.60
Purchase #2	$169.51	6.832%	$181.0909	$181.09	$181.10	$181.10
Purchase #3	$84.30	7.484%	$90.609	$90.61	$90.60	$90.60
Purchase #4	$179.74	8.455%	$194.937	$194.94	$194.95	$194.90
Purchase #5	$41.26	5.368%	$43.4748	$43.47	$43.45	$43.50
Purchase #6	$160.67	13.449%	$182.2785	$182.28	$182.30	$182.30
Purchase #7	$39.62	7.703%	$42.6719	$42.67	$42.65	$42.70
7 purchase totals =	$917.43		$1,003.6679	$1,003.67	$1,003.65	$1,003.70