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 $87.66   8.663%   $95.254   $95.25   $95.25   $95.30  
  Purchase #2 $64.30   9.174%   $70.1989   $70.20   $70.20   $70.20  
  Purchase #3 $177.51   6.426%   $188.9168   $188.92   $188.90   $188.90  
  Purchase #4 $123.61   9.575%   $135.4457   $135.45   $135.45   $135.40  
  Purchase #5 $98.96   3.836%   $102.7561   $102.76   $102.75   $102.80  
  Purchase #6 $105.73   3.805%   $109.753   $109.75   $109.75   $109.80  
  Purchase #7 $67.70   9.484%   $74.1207   $74.12   $74.10   $74.10  
  7 purchase totals = $725.47       $776.4452   $776.45   $776.40   $776.50