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 $204.62   11.294%   $227.7298   $227.73   $227.75   $227.70  
  Purchase #2 $93.29   9.736%   $102.3727   $102.37   $102.35   $102.40  
  Purchase #3 $27.26   12.535%   $30.677   $30.68   $30.70   $30.70  
  Purchase #4 $150.44   3.490%   $155.6904   $155.69   $155.70   $155.70  
  Purchase #5 $166.31   5.119%   $174.8234   $174.82   $174.80   $174.80  
  Purchase #6 $147.46   12.762%   $166.2788   $166.28   $166.30   $166.30  
  Purchase #7 $213.39   11.259%   $237.4156   $237.42   $237.40   $237.40  
  7 purchase totals = $1,002.77       $1,094.9877   $1,094.99   $1,095.00   $1,095.00