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 $85.83   13.322%   $97.2643   $97.26   $97.25   $97.30  
  Purchase #2 $204.87   5.538%   $216.2157   $216.22   $216.20   $216.20  
  Purchase #3 $109.89   11.850%   $122.912   $122.91   $122.90   $122.90  
  Purchase #4 $189.95   12.479%   $213.6539   $213.65   $213.65   $213.70  
  Purchase #5 $244.81   10.601%   $270.7623   $270.76   $270.75   $270.80  
  Purchase #6 $10.33   7.451%   $11.0997   $11.10   $11.10   $11.10  
  Purchase #7 $222.59   13.319%   $252.2368   $252.24   $252.25   $252.20  
  7 purchase totals = $1,068.27       $1,184.1447   $1,184.14   $1,184.10   $1,184.20