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 $209.66   12.412%   $235.683   $235.68   $235.70   $235.70  
  Purchase #2 $74.32   4.644%   $77.7714   $77.77   $77.75   $77.80  
  Purchase #3 $105.83   8.665%   $115.0002   $115.00   $115.00   $115.00  
  Purchase #4 $187.54   11.362%   $208.8483   $208.85   $208.85   $208.80  
  Purchase #5 $204.52   11.299%   $227.6287   $227.63   $227.65   $227.60  
  Purchase #6 $160.78   12.578%   $181.0029   $181.00   $181.00   $181.00  
  Purchase #7 $139.27   6.547%   $148.388   $148.39   $148.40   $148.40  
  7 purchase totals = $1,081.92       $1,194.3225   $1,194.32   $1,194.35   $1,194.30