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 $56.33   10.119%   $62.03   $62.03   $62.05   $62.00  
  Purchase #2 $186.73   9.545%   $204.5534   $204.55   $204.55   $204.60  
  Purchase #3 $191.62   6.798%   $204.6463   $204.65   $204.65   $204.60  
  Purchase #4 $243.38   4.834%   $255.145   $255.15   $255.15   $255.10  
  Purchase #5 $74.58   12.460%   $83.8727   $83.87   $83.85   $83.90  
  Purchase #6 $183.64   11.465%   $204.6943   $204.69   $204.70   $204.70  
  Purchase #7 $31.66   6.615%   $33.7543   $33.75   $33.75   $33.80  
  7 purchase totals = $967.94       $1,048.6960   $1,048.69   $1,048.70   $1,048.70