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 $38.70   11.611%   $43.1935   $43.19   $43.20   $43.20  
  Purchase #2 $55.98   5.724%   $59.1843   $59.18   $59.20   $59.20  
  Purchase #3 $196.62   11.370%   $218.9757   $218.98   $219.00   $219.00  
  Purchase #4 $217.42   8.705%   $236.3464   $236.35   $236.35   $236.30  
  Purchase #5 $232.93   3.806%   $241.7953   $241.80   $241.80   $241.80  
  Purchase #6 $120.82   4.654%   $126.443   $126.44   $126.45   $126.40  
  Purchase #7 $222.46   8.576%   $241.5382   $241.54   $241.55   $241.50  
  7 purchase totals = $1,084.93       $1,167.4764   $1,167.48   $1,167.55   $1,167.40