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 $41.39   8.572%   $44.938   $44.94   $44.95   $44.90  
  Purchase #2 $218.88   6.165%   $232.374   $232.37   $232.35   $232.40  
  Purchase #3 $56.53   13.500%   $64.1616   $64.16   $64.15   $64.20  
  Purchase #4 $166.58   12.381%   $187.2043   $187.20   $187.20   $187.20  
  Purchase #5 $147.75   5.477%   $155.8423   $155.84   $155.85   $155.80  
  Purchase #6 $229.51   12.253%   $257.6319   $257.63   $257.65   $257.60  
  Purchase #7 $83.71   8.385%   $90.7291   $90.73   $90.75   $90.70  
  7 purchase totals = $944.35       $1,032.8812   $1,032.87   $1,032.90   $1,032.80