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 $85.90   10.598%   $95.0037   $95.00   $95.00   $95.00  
  Purchase #2 $208.78   13.558%   $237.0864   $237.09   $237.10   $237.10  
  Purchase #3 $176.88   8.350%   $191.6495   $191.65   $191.65   $191.60  
  Purchase #4 $139.93   9.538%   $153.2765   $153.28   $153.30   $153.30  
  Purchase #5 $203.29   10.816%   $225.2778   $225.28   $225.30   $225.30  
  Purchase #6 $106.61   6.339%   $113.368   $113.37   $113.35   $113.40  
  Purchase #7 $13.99   9.669%   $15.3427   $15.34   $15.35   $15.30  
  7 purchase totals = $935.38       $1,031.0046   $1,031.01   $1,031.05   $1,031.00