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 $57.44   9.631%   $62.972   $62.97   $62.95   $63.00  
  Purchase #2 $205.72   12.646%   $231.7354   $231.74   $231.75   $231.70  
  Purchase #3 $102.39   6.308%   $108.8488   $108.85   $108.85   $108.80  
  Purchase #4 $180.39   13.622%   $204.9627   $204.96   $204.95   $205.00  
  Purchase #5 $114.61   9.715%   $125.7444   $125.74   $125.75   $125.70  
  Purchase #6 $170.28   5.117%   $178.9932   $178.99   $179.00   $179.00  
  Purchase #7 $183.71   6.446%   $195.5519   $195.55   $195.55   $195.60  
  7 purchase totals = $1,014.54       $1,108.8084   $1,108.80   $1,108.80   $1,108.80