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 $32.47   10.108%   $35.7521   $35.75   $35.75   $35.80  
  Purchase #2 $195.94   11.315%   $218.1106   $218.11   $218.10   $218.10  
  Purchase #3 $160.60   8.635%   $174.4678   $174.47   $174.45   $174.50  
  Purchase #4 $133.94   7.201%   $143.585   $143.59   $143.60   $143.60  
  Purchase #5 $15.51   13.269%   $17.568   $17.57   $17.55   $17.60  
  Purchase #6 $88.90   8.215%   $96.2031   $96.20   $96.20   $96.20  
  Purchase #7 $74.46   9.853%   $81.7965   $81.80   $81.80   $81.80  
  7 purchase totals = $701.82       $767.4831   $767.49   $767.45   $767.60