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 $211.25   11.360%   $235.248   $235.25   $235.25   $235.20  
  Purchase #2 $119.70   3.754%   $124.1935   $124.19   $124.20   $124.20  
  Purchase #3 $80.29   13.129%   $90.8313   $90.83   $90.85   $90.80  
  Purchase #4 $231.65   8.685%   $251.7688   $251.77   $251.75   $251.80  
  Purchase #5 $15.96   10.724%   $17.6716   $17.67   $17.65   $17.70  
  Purchase #6 $194.44   13.384%   $220.4638   $220.46   $220.45   $220.50  
  Purchase #7 $160.95   8.132%   $174.0385   $174.04   $174.05   $174.00  
  7 purchase totals = $1,014.24       $1,114.2155   $1,114.21   $1,114.20   $1,114.20