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 $197.44   13.827%   $224.74   $224.74   $224.75   $224.70  
  Purchase #2 $223.89   10.817%   $248.1082   $248.11   $248.10   $248.10  
  Purchase #3 $151.95   10.374%   $167.7133   $167.71   $167.70   $167.70  
  Purchase #4 $26.84   9.291%   $29.3337   $29.33   $29.35   $29.30  
  Purchase #5 $250.87   9.597%   $274.946   $274.95   $274.95   $274.90  
  Purchase #6 $30.72   10.729%   $34.0159   $34.02   $34.00   $34.00  
  Purchase #7 $195.25   10.591%   $215.9289   $215.93   $215.95   $215.90  
  7 purchase totals = $1,076.96       $1,194.7860   $1,194.79   $1,194.80   $1,194.60