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 $43.82   10.531%   $48.4347   $48.43   $48.45   $48.40  
  Purchase #2 $126.57   4.544%   $132.3213   $132.32   $132.30   $132.30  
  Purchase #3 $154.30   10.446%   $170.4182   $170.42   $170.40   $170.40  
  Purchase #4 $192.73   7.859%   $207.8767   $207.88   $207.90   $207.90  
  Purchase #5 $235.74   9.292%   $257.645   $257.65   $257.65   $257.60  
  Purchase #6 $127.32   12.326%   $143.0135   $143.01   $143.00   $143.00  
  Purchase #7 $177.57   13.122%   $200.8707   $200.87   $200.85   $200.90  
  7 purchase totals = $1,058.05       $1,160.5801   $1,160.58   $1,160.55   $1,160.50