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 $67.29   8.693%   $73.1395   $73.14   $73.15   $73.10  
  Purchase #2 $218.77   3.129%   $225.6153   $225.62   $225.60   $225.60  
  Purchase #3 $247.78   4.545%   $259.0416   $259.04   $259.05   $259.00  
  Purchase #4 $135.88   12.657%   $153.0783   $153.08   $153.10   $153.10  
  Purchase #5 $177.34   11.630%   $197.9646   $197.96   $197.95   $198.00  
  Purchase #6 $178.33   9.195%   $194.7274   $194.73   $194.75   $194.70  
  Purchase #7 $217.54   9.617%   $238.4608   $238.46   $238.45   $238.50  
  7 purchase totals = $1,242.93       $1,342.0275   $1,342.03   $1,342.05   $1,342.00