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 $88.57   7.326%   $95.0586   $95.06   $95.05   $95.10  
  Purchase #2 $242.47   9.801%   $266.2345   $266.23   $266.25   $266.20  
  Purchase #3 $211.93   9.646%   $232.3728   $232.37   $232.35   $232.40  
  Purchase #4 $194.67   4.754%   $203.9246   $203.92   $203.90   $203.90  
  Purchase #5 $202.68   3.792%   $210.3656   $210.37   $210.35   $210.40  
  Purchase #6 $58.36   13.845%   $66.4399   $66.44   $66.45   $66.40  
  Purchase #7 $204.87   3.275%   $211.5795   $211.58   $211.60   $211.60  
  7 purchase totals = $1,203.55       $1,285.9755   $1,285.97   $1,285.95   $1,286.00