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 $58.60   12.533%   $65.9443   $65.94   $65.95   $65.90  
  Purchase #2 $245.25   9.426%   $268.3673   $268.37   $268.35   $268.40  
  Purchase #3 $239.69   13.460%   $271.9523   $271.95   $271.95   $272.00  
  Purchase #4 $69.51   8.329%   $75.2995   $75.30   $75.30   $75.30  
  Purchase #5 $189.72   8.632%   $206.0966   $206.10   $206.10   $206.10  
  Purchase #6 $66.94   7.182%   $71.7476   $71.75   $71.75   $71.70  
  Purchase #7 $168.67   8.292%   $182.6561   $182.66   $182.65   $182.70  
  7 purchase totals = $1,038.38       $1,142.0637   $1,142.07   $1,142.05   $1,142.10