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 $78.62   5.818%   $83.1941   $83.19   $83.20   $83.20  
  Purchase #2 $179.89   8.376%   $194.9576   $194.96   $194.95   $195.00  
  Purchase #3 $208.89   12.469%   $234.9365   $234.94   $234.95   $234.90  
  Purchase #4 $92.73   7.484%   $99.6699   $99.67   $99.65   $99.70  
  Purchase #5 $182.52   13.104%   $206.4374   $206.44   $206.45   $206.40  
  Purchase #6 $210.68   10.250%   $232.2747   $232.27   $232.25   $232.30  
  Purchase #7 $22.26   5.568%   $23.4994   $23.50   $23.50   $23.50  
  7 purchase totals = $975.59       $1,074.9696   $1,074.97   $1,074.95   $1,075.00