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 $41.42   6.352%   $44.051   $44.05   $44.05   $44.10  
  Purchase #2 $241.55   6.515%   $257.287   $257.29   $257.30   $257.30  
  Purchase #3 $192.36   5.869%   $203.6496   $203.65   $203.65   $203.60  
  Purchase #4 $24.42   10.533%   $26.9922   $26.99   $27.00   $27.00  
  Purchase #5 $85.35   6.863%   $91.2076   $91.21   $91.20   $91.20  
  Purchase #6 $235.55   12.826%   $265.7616   $265.76   $265.75   $265.80  
  Purchase #7 $186.39   10.439%   $205.8473   $205.85   $205.85   $205.80  
  7 purchase totals = $1,007.04       $1,094.7963   $1,094.80   $1,094.80   $1,094.80