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 $57.55   8.212%   $62.276   $62.28   $62.30   $62.30  
  Purchase #2 $139.64   4.588%   $146.0467   $146.05   $146.05   $146.00  
  Purchase #3 $208.82   6.764%   $222.9446   $222.94   $222.95   $222.90  
  Purchase #4 $211.67   5.209%   $222.6959   $222.70   $222.70   $222.70  
  Purchase #5 $193.32   5.688%   $204.316   $204.32   $204.30   $204.30  
  Purchase #6 $224.89   7.506%   $241.7702   $241.77   $241.75   $241.80  
  Purchase #7 $82.25   4.689%   $86.1067   $86.11   $86.10   $86.10  
  7 purchase totals = $1,118.14       $1,186.1561   $1,186.17   $1,186.15   $1,186.10