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 $57.86   8.130%   $62.564   $62.56   $62.55   $62.60  
  Purchase #2 $154.85   3.764%   $160.6786   $160.68   $160.70   $160.70  
  Purchase #3 $101.37   9.248%   $110.7447   $110.74   $110.75   $110.70  
  Purchase #4 $24.46   13.458%   $27.7518   $27.75   $27.75   $27.80  
  Purchase #5 $215.35   7.817%   $232.1839   $232.18   $232.20   $232.20  
  Purchase #6 $227.51   6.651%   $242.6417   $242.64   $242.65   $242.60  
  Purchase #7 $123.45   10.488%   $136.3974   $136.40   $136.40   $136.40  
  7 purchase totals = $904.85       $972.9621   $972.95   $973.00   $973.00