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 $197.80   6.658%   $210.9695   $210.97   $210.95   $211.00  
  Purchase #2 $226.81   8.599%   $246.3134   $246.31   $246.30   $246.30  
  Purchase #3 $95.73   8.819%   $104.1724   $104.17   $104.15   $104.20  
  Purchase #4 $165.49   3.871%   $171.8961   $171.90   $171.90   $171.90  
  Purchase #5 $17.83   9.759%   $19.57   $19.57   $19.55   $19.60  
  Purchase #6 $220.97   6.464%   $235.2535   $235.25   $235.25   $235.30  
  Purchase #7 $206.44   3.531%   $213.7294   $213.73   $213.75   $213.70  
  7 purchase totals = $1,131.07       $1,201.9043   $1,201.90   $1,201.85   $1,202.00