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 $224.97   7.202%   $241.1723   $241.17   $241.15   $241.20  
  Purchase #2 $236.28   7.619%   $254.2822   $254.28   $254.30   $254.30  
  Purchase #3 $95.83   8.198%   $103.6861   $103.69   $103.70   $103.70  
  Purchase #4 $36.27   3.227%   $37.4404   $37.44   $37.45   $37.40  
  Purchase #5 $182.45   10.143%   $200.9559   $200.96   $200.95   $201.00  
  Purchase #6 $74.29   13.829%   $84.5636   $84.56   $84.55   $84.60  
  Purchase #7 $241.28   6.502%   $256.968   $256.97   $256.95   $257.00  
  7 purchase totals = $1,091.37       $1,179.0685   $1,179.07   $1,179.05   $1,179.20