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 $89.68   6.597%   $95.5962   $95.60   $95.60   $95.60  
  Purchase #2 $177.87   9.730%   $195.1768   $195.18   $195.20   $195.20  
  Purchase #3 $43.96   7.436%   $47.2289   $47.23   $47.25   $47.20  
  Purchase #4 $103.51   6.625%   $110.3675   $110.37   $110.35   $110.40  
  Purchase #5 $180.26   12.249%   $202.34   $202.34   $202.35   $202.30  
  Purchase #6 $250.54   13.234%   $283.6965   $283.70   $283.70   $283.70  
  Purchase #7 $130.83   7.432%   $140.5533   $140.55   $140.55   $140.60  
  7 purchase totals = $976.65       $1,074.9592   $1,074.97   $1,075.00   $1,075.00