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 $175.56   11.512%   $195.7705   $195.77   $195.75   $195.80  
  Purchase #2 $200.93   9.819%   $220.6593   $220.66   $220.65   $220.70  
  Purchase #3 $58.95   3.773%   $61.1742   $61.17   $61.15   $61.20  
  Purchase #4 $67.65   7.746%   $72.8902   $72.89   $72.90   $72.90  
  Purchase #5 $207.95   13.391%   $235.7966   $235.80   $235.80   $235.80  
  Purchase #6 $234.79   5.156%   $246.8958   $246.90   $246.90   $246.90  
  Purchase #7 $177.77   8.681%   $193.2022   $193.20   $193.20   $193.20  
  7 purchase totals = $1,123.60       $1,226.3888   $1,226.39   $1,226.35   $1,226.50