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 $115.55   8.193%   $125.017   $125.02   $125.00   $125.00  
  Purchase #2 $52.82   3.478%   $54.6571   $54.66   $54.65   $54.70  
  Purchase #3 $170.98   11.829%   $191.2052   $191.21   $191.20   $191.20  
  Purchase #4 $112.75   3.784%   $117.0165   $117.02   $117.00   $117.00  
  Purchase #5 $185.78   6.271%   $197.4303   $197.43   $197.45   $197.40  
  Purchase #6 $86.55   5.615%   $91.4098   $91.41   $91.40   $91.40  
  Purchase #7 $236.33   5.182%   $248.5766   $248.58   $248.60   $248.60  
  7 purchase totals = $960.76       $1,025.3125   $1,025.33   $1,025.30   $1,025.30