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 $77.25   12.595%   $86.9796   $86.98   $87.00   $87.00  
  Purchase #2 $161.41   5.788%   $170.7524   $170.75   $170.75   $170.80  
  Purchase #3 $127.66   3.426%   $132.0336   $132.03   $132.05   $132.00  
  Purchase #4 $83.49   11.329%   $92.9486   $92.95   $92.95   $92.90  
  Purchase #5 $118.66   4.133%   $123.5642   $123.56   $123.55   $123.60  
  Purchase #6 $176.46   10.175%   $194.4148   $194.41   $194.40   $194.40  
  Purchase #7 $195.92   7.458%   $210.5317   $210.53   $210.55   $210.50  
  7 purchase totals = $940.85       $1,011.2249   $1,011.21   $1,011.25   $1,011.20