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 $85.55   7.247%   $91.7498   $91.75   $91.75   $91.70  
  Purchase #2 $113.92   11.262%   $126.7497   $126.75   $126.75   $126.70  
  Purchase #3 $18.34   12.543%   $20.6404   $20.64   $20.65   $20.60  
  Purchase #4 $58.90   3.386%   $60.8944   $60.89   $60.90   $60.90  
  Purchase #5 $83.35   13.828%   $94.8756   $94.88   $94.90   $94.90  
  Purchase #6 $201.53   4.293%   $210.1817   $210.18   $210.20   $210.20  
  Purchase #7 $133.77   10.327%   $147.5844   $147.58   $147.60   $147.60  
  7 purchase totals = $695.36       $752.6760   $752.67   $752.75   $752.60