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 $126.69   5.557%   $133.7302   $133.73   $133.75   $133.70  
  Purchase #2 $31.90   10.566%   $35.2706   $35.27   $35.25   $35.30  
  Purchase #3 $30.34   7.472%   $32.607   $32.61   $32.60   $32.60  
  Purchase #4 $143.30   6.289%   $152.3121   $152.31   $152.30   $152.30  
  Purchase #5 $186.94   8.469%   $202.7719   $202.77   $202.75   $202.80  
  Purchase #6 $192.58   5.431%   $203.039   $203.04   $203.05   $203.00  
  Purchase #7 $172.51   13.377%   $195.5867   $195.59   $195.60   $195.60  
  7 purchase totals = $884.26       $955.3175   $955.32   $955.30   $955.30