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 $55.82   9.187%   $60.9482   $60.95   $60.95   $60.90  
  Purchase #2 $237.51   11.841%   $265.6336   $265.63   $265.65   $265.60  
  Purchase #3 $161.82   9.694%   $177.5068   $177.51   $177.50   $177.50  
  Purchase #4 $230.51   10.709%   $255.1953   $255.20   $255.20   $255.20  
  Purchase #5 $103.88   6.855%   $111.001   $111.00   $111.00   $111.00  
  Purchase #6 $90.54   13.425%   $102.695   $102.70   $102.70   $102.70  
  Purchase #7 $34.34   9.640%   $37.6504   $37.65   $37.65   $37.70  
  7 purchase totals = $914.42       $1,010.6303   $1,010.64   $1,010.65   $1,010.60