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 $114.92   8.823%   $125.0594   $125.06   $125.05   $125.10  
  Purchase #2 $183.42   8.303%   $198.6494   $198.65   $198.65   $198.60  
  Purchase #3 $181.82   8.776%   $197.7765   $197.78   $197.80   $197.80  
  Purchase #4 $193.57   10.703%   $214.2878   $214.29   $214.30   $214.30  
  Purchase #5 $89.75   13.636%   $101.9883   $101.99   $102.00   $102.00  
  Purchase #6 $178.55   12.542%   $200.9437   $200.94   $200.95   $200.90  
  Purchase #7 $79.62   8.255%   $86.1926   $86.19   $86.20   $86.20  
  7 purchase totals = $1,021.65       $1,124.8977   $1,124.90   $1,124.95   $1,124.90