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 $205.87   4.489%   $215.1115   $215.11   $215.10   $215.10  
  Purchase #2 $236.46   11.861%   $264.5065   $264.51   $264.50   $264.50  
  Purchase #3 $61.52   3.523%   $63.6873   $63.69   $63.70   $63.70  
  Purchase #4 $222.32   3.336%   $229.7366   $229.74   $229.75   $229.70  
  Purchase #5 $19.91   10.342%   $21.9691   $21.97   $21.95   $22.00  
  Purchase #6 $122.79   12.775%   $138.4764   $138.48   $138.50   $138.50  
  Purchase #7 $60.34   10.759%   $66.832   $66.83   $66.85   $66.80  
  7 purchase totals = $929.21       $1,000.3194   $1,000.33   $1,000.35   $1,000.30