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 $210.65   12.483%   $236.9454   $236.95   $236.95   $236.90  
  Purchase #2 $181.92   8.552%   $197.4778   $197.48   $197.50   $197.50  
  Purchase #3 $45.49   8.654%   $49.4267   $49.43   $49.45   $49.40  
  Purchase #4 $79.42   5.248%   $83.588   $83.59   $83.60   $83.60  
  Purchase #5 $23.95   4.218%   $24.9602   $24.96   $24.95   $25.00  
  Purchase #6 $168.93   12.641%   $190.2844   $190.28   $190.30   $190.30  
  Purchase #7 $82.73   12.629%   $93.178   $93.18   $93.20   $93.20  
  7 purchase totals = $793.09       $875.8605   $875.87   $875.95   $875.90