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 $87.51   5.780%   $92.5681   $92.57   $92.55   $92.60  
  Purchase #2 $185.62   4.207%   $193.429   $193.43   $193.45   $193.40  
  Purchase #3 $144.69   6.873%   $154.6345   $154.63   $154.65   $154.60  
  Purchase #4 $83.26   6.856%   $88.9683   $88.97   $88.95   $89.00  
  Purchase #5 $191.53   13.522%   $217.4287   $217.43   $217.45   $217.40  
  Purchase #6 $214.43   9.467%   $234.7301   $234.73   $234.75   $234.70  
  Purchase #7 $76.54   4.767%   $80.1887   $80.19   $80.20   $80.20  
  7 purchase totals = $983.58       $1,061.9474   $1,061.95   $1,062.00   $1,061.90