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 $201.77   4.702%   $211.2572   $211.26   $211.25   $211.30  
  Purchase #2 $66.42   9.345%   $72.6269   $72.63   $72.65   $72.60  
  Purchase #3 $237.34   13.720%   $269.903   $269.90   $269.90   $269.90  
  Purchase #4 $64.81   7.523%   $69.6857   $69.69   $69.70   $69.70  
  Purchase #5 $21.94   13.490%   $24.8997   $24.90   $24.90   $24.90  
  Purchase #6 $166.80   12.350%   $187.3998   $187.40   $187.40   $187.40  
  Purchase #7 $168.67   4.792%   $176.7527   $176.75   $176.75   $176.80  
  7 purchase totals = $927.75       $1,012.5250   $1,012.53   $1,012.55   $1,012.60