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 $114.30   10.109%   $125.8546   $125.85   $125.85   $125.90  
  Purchase #2 $246.49   4.821%   $258.3733   $258.37   $258.35   $258.40  
  Purchase #3 $92.43   5.229%   $97.2632   $97.26   $97.25   $97.30  
  Purchase #4 $243.96   10.329%   $269.1586   $269.16   $269.15   $269.20  
  Purchase #5 $212.56   5.676%   $224.6249   $224.62   $224.60   $224.60  
  Purchase #6 $244.89   13.265%   $277.3747   $277.37   $277.35   $277.40  
  Purchase #7 $171.94   4.365%   $179.4452   $179.45   $179.45   $179.40  
  7 purchase totals = $1,326.57       $1,432.0945   $1,432.08   $1,432.00   $1,432.20