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 $216.85   8.812%   $235.9588   $235.96   $235.95   $236.00  
  Purchase #2 $152.82   3.137%   $157.614   $157.61   $157.60   $157.60  
  Purchase #3 $105.56   13.206%   $119.5003   $119.50   $119.50   $119.50  
  Purchase #4 $70.83   9.570%   $77.6084   $77.61   $77.60   $77.60  
  Purchase #5 $101.87   11.682%   $113.7705   $113.77   $113.75   $113.80  
  Purchase #6 $243.64   4.874%   $255.515   $255.52   $255.50   $255.50  
  Purchase #7 $228.42   6.542%   $243.3632   $243.36   $243.35   $243.40  
  7 purchase totals = $1,119.99       $1,203.3302   $1,203.33   $1,203.25   $1,203.40