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 $182.29   5.132%   $191.6451   $191.65   $191.65   $191.60  
  Purchase #2 $16.53   3.198%   $17.0586   $17.06   $17.05   $17.10  
  Purchase #3 $60.91   3.459%   $63.0169   $63.02   $63.00   $63.00  
  Purchase #4 $49.41   12.383%   $55.5284   $55.53   $55.55   $55.50  
  Purchase #5 $175.55   11.708%   $196.1034   $196.10   $196.10   $196.10  
  Purchase #6 $102.76   5.589%   $108.5033   $108.50   $108.50   $108.50  
  Purchase #7 $117.65   7.179%   $126.0961   $126.10   $126.10   $126.10  
  7 purchase totals = $705.10       $757.9518   $757.96   $757.95   $757.90