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 $215.77   8.703%   $234.5485   $234.55   $234.55   $234.50  
  Purchase #2 $178.81   10.254%   $197.1452   $197.15   $197.15   $197.10  
  Purchase #3 $24.57   3.467%   $25.4218   $25.42   $25.40   $25.40  
  Purchase #4 $234.47   5.662%   $247.7457   $247.75   $247.75   $247.70  
  Purchase #5 $123.37   9.716%   $135.3566   $135.36   $135.35   $135.40  
  Purchase #6 $180.69   12.663%   $203.5708   $203.57   $203.55   $203.60  
  Purchase #7 $7.58   13.534%   $8.6059   $8.61   $8.60   $8.60  
  7 purchase totals = $965.26       $1,052.3945   $1,052.41   $1,052.35   $1,052.30