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 $161.71   9.195%   $176.5792   $176.58   $176.60   $176.60  
  Purchase #2 $25.89   4.625%   $27.0874   $27.09   $27.10   $27.10  
  Purchase #3 $160.78   5.406%   $169.4718   $169.47   $169.45   $169.50  
  Purchase #4 $185.42   7.329%   $199.0094   $199.01   $199.00   $199.00  
  Purchase #5 $122.31   11.633%   $136.5383   $136.54   $136.55   $136.50  
  Purchase #6 $217.94   7.165%   $233.5554   $233.56   $233.55   $233.60  
  Purchase #7 $73.75   9.360%   $80.653   $80.65   $80.65   $80.70  
  7 purchase totals = $947.80       $1,022.8945   $1,022.90   $1,022.90   $1,023.00