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 $84.58   13.216%   $95.7581   $95.76   $95.75   $95.80  
  Purchase #2 $117.69   3.820%   $122.1858   $122.19   $122.20   $122.20  
  Purchase #3 $208.46   9.359%   $227.9698   $227.97   $227.95   $228.00  
  Purchase #4 $189.67   12.281%   $212.9634   $212.96   $212.95   $213.00  
  Purchase #5 $70.36   7.360%   $75.5385   $75.54   $75.55   $75.50  
  Purchase #6 $174.36   9.640%   $191.1683   $191.17   $191.15   $191.20  
  Purchase #7 $104.97   4.867%   $110.0789   $110.08   $110.10   $110.10  
  7 purchase totals = $950.09       $1,035.6628   $1,035.67   $1,035.65   $1,035.80