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 $225.96   5.202%   $237.7144   $237.71   $237.70   $237.70  
  Purchase #2 $235.82   11.201%   $262.2342   $262.23   $262.25   $262.20  
  Purchase #3 $246.74   5.265%   $259.7309   $259.73   $259.75   $259.70  
  Purchase #4 $75.39   6.741%   $80.472   $80.47   $80.45   $80.50  
  Purchase #5 $14.65   5.286%   $15.4244   $15.42   $15.40   $15.40  
  Purchase #6 $40.86   6.814%   $43.6442   $43.64   $43.65   $43.60  
  Purchase #7 $113.35   8.691%   $123.2012   $123.20   $123.20   $123.20  
  7 purchase totals = $952.77       $1,022.4213   $1,022.40   $1,022.40   $1,022.30