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 $58.87   4.510%   $61.525   $61.53   $61.55   $61.50  
  Purchase #2 $141.53   13.277%   $160.3209   $160.32   $160.30   $160.30  
  Purchase #3 $22.85   9.668%   $25.0591   $25.06   $25.05   $25.10  
  Purchase #4 $186.98   5.198%   $196.6992   $196.70   $196.70   $196.70  
  Purchase #5 $170.89   3.406%   $176.7105   $176.71   $176.70   $176.70  
  Purchase #6 $250.60   6.527%   $266.9567   $266.96   $266.95   $267.00  
  Purchase #7 $103.86   4.771%   $108.8152   $108.82   $108.80   $108.80  
  7 purchase totals = $935.58       $996.0866   $996.10   $996.05   $996.10