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 $44.48   10.326%   $49.073   $49.07   $49.05   $49.10  
  Purchase #2 $218.33   8.487%   $236.8597   $236.86   $236.85   $236.90  
  Purchase #3 $111.30   8.341%   $120.5835   $120.58   $120.60   $120.60  
  Purchase #4 $28.54   10.828%   $31.6303   $31.63   $31.65   $31.60  
  Purchase #5 $193.57   4.698%   $202.6639   $202.66   $202.65   $202.70  
  Purchase #6 $170.54   6.348%   $181.3659   $181.37   $181.35   $181.40  
  Purchase #7 $189.73   9.317%   $207.4071   $207.41   $207.40   $207.40  
  7 purchase totals = $956.49       $1,029.5834   $1,029.58   $1,029.55   $1,029.70