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 $164.49   4.381%   $171.6963   $171.70   $171.70   $171.70  
  Purchase #2 $225.87   12.735%   $254.6345   $254.63   $254.65   $254.60  
  Purchase #3 $29.76   8.146%   $32.1842   $32.18   $32.20   $32.20  
  Purchase #4 $236.58   12.825%   $266.9214   $266.92   $266.90   $266.90  
  Purchase #5 $118.97   3.500%   $123.134   $123.13   $123.15   $123.10  
  Purchase #6 $240.52   4.548%   $251.4588   $251.46   $251.45   $251.50  
  Purchase #7 $60.83   7.150%   $65.1793   $65.18   $65.20   $65.20  
  7 purchase totals = $1,077.02       $1,165.2085   $1,165.20   $1,165.25   $1,165.20