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 $224.92   7.518%   $241.8295   $241.83   $241.85   $241.80  
  Purchase #2 $228.74   10.411%   $252.5541   $252.55   $252.55   $252.60  
  Purchase #3 $183.37   5.574%   $193.591   $193.59   $193.60   $193.60  
  Purchase #4 $19.95   8.767%   $21.699   $21.70   $21.70   $21.70  
  Purchase #5 $62.37   13.768%   $70.9571   $70.96   $70.95   $71.00  
  Purchase #6 $57.57   6.250%   $61.1681   $61.17   $61.15   $61.20  
  Purchase #7 $10.61   7.250%   $11.3792   $11.38   $11.40   $11.40  
  7 purchase totals = $787.53       $853.1780   $853.18   $853.20   $853.30