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 $211.60   11.142%   $235.1765   $235.18   $235.20   $235.20  
  Purchase #2 $78.41   8.608%   $85.1595   $85.16   $85.15   $85.20  
  Purchase #3 $161.42   7.312%   $173.223   $173.22   $173.20   $173.20  
  Purchase #4 $200.66   5.764%   $212.226   $212.23   $212.25   $212.20  
  Purchase #5 $114.80   3.439%   $118.748   $118.75   $118.75   $118.70  
  Purchase #6 $236.88   7.169%   $253.8619   $253.86   $253.85   $253.90  
  Purchase #7 $90.37   13.774%   $102.8176   $102.82   $102.80   $102.80  
  7 purchase totals = $1,094.14       $1,181.2125   $1,181.22   $1,181.20   $1,181.20