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 $43.96   8.373%   $47.6408   $47.64   $47.65   $47.60  
  Purchase #2 $151.71   8.534%   $164.6569   $164.66   $164.65   $164.70  
  Purchase #3 $240.96   9.544%   $263.9572   $263.96   $263.95   $264.00  
  Purchase #4 $235.40   9.738%   $258.3233   $258.32   $258.30   $258.30  
  Purchase #5 $229.43   9.280%   $250.7211   $250.72   $250.70   $250.70  
  Purchase #6 $154.73   8.411%   $167.7443   $167.74   $167.75   $167.70  
  Purchase #7 $110.84   13.167%   $125.4343   $125.43   $125.45   $125.40  
  7 purchase totals = $1,167.03       $1,278.4779   $1,278.47   $1,278.45   $1,278.40