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 $192.32   4.515%   $201.0032   $201.00   $201.00   $201.00  
  Purchase #2 $38.26   3.371%   $39.5497   $39.55   $39.55   $39.50  
  Purchase #3 $204.53   4.238%   $213.198   $213.20   $213.20   $213.20  
  Purchase #4 $101.30   11.475%   $112.9242   $112.92   $112.90   $112.90  
  Purchase #5 $235.81   7.163%   $252.7011   $252.70   $252.70   $252.70  
  Purchase #6 $151.53   5.528%   $159.9066   $159.91   $159.90   $159.90  
  Purchase #7 $201.53   3.854%   $209.297   $209.30   $209.30   $209.30  
  7 purchase totals = $1,125.28       $1,188.5798   $1,188.58   $1,188.55   $1,188.50