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 $235.58   11.278%   $262.1487   $262.15   $262.15   $262.10  
  Purchase #2 $218.33   4.835%   $228.8863   $228.89   $228.90   $228.90  
  Purchase #3 $68.57   10.412%   $75.7095   $75.71   $75.70   $75.70  
  Purchase #4 $217.44   8.275%   $235.4332   $235.43   $235.45   $235.40  
  Purchase #5 $127.45   11.406%   $141.9869   $141.99   $142.00   $142.00  
  Purchase #6 $204.43   8.850%   $222.5221   $222.52   $222.50   $222.50  
  Purchase #7 $24.37   6.190%   $25.8785   $25.88   $25.90   $25.90  
  7 purchase totals = $1,096.17       $1,192.5652   $1,192.57   $1,192.60   $1,192.50