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 $41.42   5.659%   $43.764   $43.76   $43.75   $43.80  
  Purchase #2 $235.72   5.388%   $248.4206   $248.42   $248.40   $248.40  
  Purchase #3 $228.95   5.380%   $241.2675   $241.27   $241.25   $241.30  
  Purchase #4 $61.73   6.320%   $65.6313   $65.63   $65.65   $65.60  
  Purchase #5 $28.54   10.494%   $31.535   $31.54   $31.55   $31.50  
  Purchase #6 $84.25   10.451%   $93.055   $93.06   $93.05   $93.10  
  Purchase #7 $150.36   3.192%   $155.1595   $155.16   $155.15   $155.20  
  7 purchase totals = $830.97       $878.8329   $878.84   $878.80   $878.90