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 $232.75   12.580%   $262.03   $262.03   $262.05   $262.00  
  Purchase #2 $166.81   6.625%   $177.8612   $177.86   $177.85   $177.90  
  Purchase #3 $69.77   8.809%   $75.916   $75.92   $75.90   $75.90  
  Purchase #4 $134.51   6.859%   $143.736   $143.74   $143.75   $143.70  
  Purchase #5 $233.73   3.341%   $241.5389   $241.54   $241.55   $241.50  
  Purchase #6 $18.50   9.466%   $20.2512   $20.25   $20.25   $20.30  
  Purchase #7 $38.92   7.141%   $41.6993   $41.70   $41.70   $41.70  
  7 purchase totals = $894.99       $963.0326   $963.04   $963.05   $963.00