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 $113.31   5.604%   $119.6599   $119.66   $119.65   $119.70  
  Purchase #2 $178.33   4.415%   $186.2033   $186.20   $186.20   $186.20  
  Purchase #3 $103.31   4.732%   $108.1986   $108.20   $108.20   $108.20  
  Purchase #4 $48.76   6.106%   $51.7373   $51.74   $51.75   $51.70  
  Purchase #5 $66.35   9.627%   $72.7375   $72.74   $72.75   $72.70  
  Purchase #6 $26.75   3.301%   $27.633   $27.63   $27.65   $27.60  
  Purchase #7 $119.84   6.330%   $127.4259   $127.43   $127.45   $127.40  
  7 purchase totals = $656.65       $693.5955   $693.60   $693.65   $693.50