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 $214.48   10.818%   $237.6824   $237.68   $237.70   $237.70  
  Purchase #2 $226.31   6.627%   $241.3076   $241.31   $241.30   $241.30  
  Purchase #3 $110.28   10.731%   $122.1141   $122.11   $122.10   $122.10  
  Purchase #4 $100.77   4.433%   $105.2371   $105.24   $105.25   $105.20  
  Purchase #5 $54.47   8.477%   $59.0874   $59.09   $59.10   $59.10  
  Purchase #6 $171.47   6.154%   $182.0223   $182.02   $182.00   $182.00  
  Purchase #7 $77.79   11.308%   $86.5865   $86.59   $86.60   $86.60  
  7 purchase totals = $955.57       $1,034.0374   $1,034.04   $1,034.05   $1,034.00