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 $91.95   3.494%   $95.1627   $95.16   $95.15   $95.20  
  Purchase #2 $72.35   3.741%   $75.0566   $75.06   $75.05   $75.10  
  Purchase #3 $151.90   8.348%   $164.5806   $164.58   $164.60   $164.60  
  Purchase #4 $152.58   12.750%   $172.034   $172.03   $172.05   $172.00  
  Purchase #5 $41.56   3.601%   $43.0566   $43.06   $43.05   $43.10  
  Purchase #6 $214.51   7.869%   $231.3898   $231.39   $231.40   $231.40  
  Purchase #7 $62.83   13.564%   $71.3523   $71.35   $71.35   $71.40  
  7 purchase totals = $787.68       $852.6326   $852.63   $852.65   $852.80