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 $88.94   6.839%   $95.0226   $95.02   $95.00   $95.00  
  Purchase #2 $191.74   9.208%   $209.3954   $209.40   $209.40   $209.40  
  Purchase #3 $191.26   8.869%   $208.2228   $208.22   $208.20   $208.20  
  Purchase #4 $53.62   8.294%   $58.0672   $58.07   $58.05   $58.10  
  Purchase #5 $23.98   7.820%   $25.8552   $25.86   $25.85   $25.90  
  Purchase #6 $137.38   5.197%   $144.5196   $144.52   $144.50   $144.50  
  Purchase #7 $242.55   9.369%   $265.2745   $265.27   $265.25   $265.30  
  7 purchase totals = $929.47       $1,006.3573   $1,006.36   $1,006.25   $1,006.40