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 $169.33   3.657%   $175.5224   $175.52   $175.50   $175.50  
  Purchase #2 $90.27   3.725%   $93.6326   $93.63   $93.65   $93.60  
  Purchase #3 $62.91   10.206%   $69.3306   $69.33   $69.35   $69.30  
  Purchase #4 $243.30   9.855%   $267.2772   $267.28   $267.30   $267.30  
  Purchase #5 $235.71   5.342%   $248.3016   $248.30   $248.30   $248.30  
  Purchase #6 $174.95   6.709%   $186.6874   $186.69   $186.70   $186.70  
  Purchase #7 $16.90   4.707%   $17.6955   $17.70   $17.70   $17.70  
  7 purchase totals = $993.37       $1,058.4473   $1,058.45   $1,058.50   $1,058.40