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 $208.58   8.601%   $226.52   $226.52   $226.50   $226.50  
  Purchase #2 $164.32   6.799%   $175.4921   $175.49   $175.50   $175.50  
  Purchase #3 $147.58   5.524%   $155.7323   $155.73   $155.75   $155.70  
  Purchase #4 $58.27   8.594%   $63.2777   $63.28   $63.30   $63.30  
  Purchase #5 $242.45   12.372%   $272.4459   $272.45   $272.45   $272.40  
  Purchase #6 $223.63   7.810%   $241.0955   $241.10   $241.10   $241.10  
  Purchase #7 $7.46   6.523%   $7.9466   $7.95   $7.95   $7.90  
  7 purchase totals = $1,052.29       $1,142.5101   $1,142.52   $1,142.55   $1,142.40