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 $84.99   11.469%   $94.7375   $94.74   $94.75   $94.70  
  Purchase #2 $205.91   10.851%   $228.2533   $228.25   $228.25   $228.30  
  Purchase #3 $240.25   9.355%   $262.7254   $262.73   $262.75   $262.70  
  Purchase #4 $115.76   8.293%   $125.36   $125.36   $125.35   $125.40  
  Purchase #5 $169.85   8.185%   $183.7522   $183.75   $183.75   $183.80  
  Purchase #6 $39.66   4.353%   $41.3864   $41.39   $41.40   $41.40  
  Purchase #7 $71.81   5.544%   $75.7911   $75.79   $75.80   $75.80  
  7 purchase totals = $928.23       $1,012.0059   $1,012.01   $1,012.05   $1,012.10