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 $84.67   12.428%   $95.1928   $95.19   $95.20   $95.20  
  Purchase #2 $188.33   12.389%   $211.6622   $211.66   $211.65   $211.70  
  Purchase #3 $147.69   8.570%   $160.347   $160.35   $160.35   $160.30  
  Purchase #4 $205.97   5.476%   $217.2489   $217.25   $217.25   $217.20  
  Purchase #5 $100.47   13.814%   $114.3489   $114.35   $114.35   $114.30  
  Purchase #6 $239.85   8.149%   $259.3954   $259.40   $259.40   $259.40  
  Purchase #7 $125.81   10.272%   $138.7332   $138.73   $138.75   $138.70  
  7 purchase totals = $1,092.79       $1,196.9284   $1,196.93   $1,196.95   $1,196.80