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 $67.53   8.384%   $73.1917   $73.19   $73.20   $73.20  
  Purchase #2 $221.34   10.624%   $244.8552   $244.86   $244.85   $244.90  
  Purchase #3 $220.90   6.260%   $234.7283   $234.73   $234.75   $234.70  
  Purchase #4 $72.58   12.189%   $81.4268   $81.43   $81.45   $81.40  
  Purchase #5 $213.37   5.493%   $225.0904   $225.09   $225.10   $225.10  
  Purchase #6 $194.99   8.221%   $211.0201   $211.02   $211.00   $211.00  
  Purchase #7 $33.36   9.579%   $36.5556   $36.56   $36.55   $36.60  
  7 purchase totals = $1,024.07       $1,106.8681   $1,106.88   $1,106.90   $1,106.90