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 $214.89   12.571%   $241.9038   $241.90   $241.90   $241.90  
  Purchase #2 $214.57   6.849%   $229.2659   $229.27   $229.25   $229.30  
  Purchase #3 $124.93   10.670%   $138.26   $138.26   $138.25   $138.30  
  Purchase #4 $149.73   3.508%   $154.9825   $154.98   $155.00   $155.00  
  Purchase #5 $7.94   8.804%   $8.639   $8.64   $8.65   $8.60  
  Purchase #6 $140.89   4.228%   $146.8468   $146.85   $146.85   $146.80  
  Purchase #7 $151.49   7.355%   $162.6321   $162.63   $162.65   $162.60  
  7 purchase totals = $1,004.44       $1,082.5301   $1,082.53   $1,082.55   $1,082.50