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 $97.35   5.542%   $102.7451   $102.75   $102.75   $102.70  
  Purchase #2 $188.32   10.638%   $208.3535   $208.35   $208.35   $208.40  
  Purchase #3 $104.86   12.790%   $118.2716   $118.27   $118.25   $118.30  
  Purchase #4 $201.52   10.294%   $222.2645   $222.26   $222.25   $222.30  
  Purchase #5 $112.86   9.201%   $123.2442   $123.24   $123.25   $123.20  
  Purchase #6 $64.47   5.477%   $68.001   $68.00   $68.00   $68.00  
  Purchase #7 $225.33   3.120%   $232.3603   $232.36   $232.35   $232.40  
  7 purchase totals = $994.71       $1,075.2402   $1,075.23   $1,075.20   $1,075.30