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 $219.88   3.513%   $227.6044   $227.60   $227.60   $227.60  
  Purchase #2 $235.66   10.583%   $260.5999   $260.60   $260.60   $260.60  
  Purchase #3 $38.79   4.140%   $40.3959   $40.40   $40.40   $40.40  
  Purchase #4 $148.31   5.231%   $156.0681   $156.07   $156.05   $156.10  
  Purchase #5 $11.42   5.359%   $12.032   $12.03   $12.05   $12.00  
  Purchase #6 $186.71   8.155%   $201.9362   $201.94   $201.95   $201.90  
  Purchase #7 $34.41   4.565%   $35.9808   $35.98   $36.00   $36.00  
  7 purchase totals = $875.18       $934.6173   $934.62   $934.65   $934.60