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 $58.89   10.690%   $65.1853   $65.19   $65.20   $65.20  
  Purchase #2 $224.35   4.796%   $235.1098   $235.11   $235.10   $235.10  
  Purchase #3 $54.81   13.735%   $62.3382   $62.34   $62.35   $62.30  
  Purchase #4 $247.88   9.200%   $270.685   $270.69   $270.70   $270.70  
  Purchase #5 $194.85   12.273%   $218.7639   $218.76   $218.75   $218.80  
  Purchase #6 $26.59   8.168%   $28.7619   $28.76   $28.75   $28.80  
  Purchase #7 $162.50   12.700%   $183.1375   $183.14   $183.15   $183.10  
  7 purchase totals = $969.87       $1,063.9816   $1,063.99   $1,064.00   $1,064.00