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 $86.47   8.762%   $94.0465   $94.05   $94.05   $94.00  
  Purchase #2 $34.62   7.177%   $37.1047   $37.10   $37.10   $37.10  
  Purchase #3 $164.88   8.626%   $179.1025   $179.10   $179.10   $179.10  
  Purchase #4 $25.69   6.179%   $27.2774   $27.28   $27.30   $27.30  
  Purchase #5 $38.32   8.546%   $41.5948   $41.59   $41.60   $41.60  
  Purchase #6 $246.85   3.125%   $254.5641   $254.56   $254.55   $254.60  
  Purchase #7 $118.37   13.400%   $134.2316   $134.23   $134.25   $134.20  
  7 purchase totals = $715.20       $767.9216   $767.91   $767.95   $767.90