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 $69.25   5.325%   $72.9376   $72.94   $72.95   $72.90  
  Purchase #2 $141.43   3.835%   $146.8538   $146.85   $146.85   $146.90  
  Purchase #3 $218.66   9.653%   $239.7672   $239.77   $239.75   $239.80  
  Purchase #4 $70.99   13.316%   $80.443   $80.44   $80.45   $80.40  
  Purchase #5 $74.59   9.613%   $81.7603   $81.76   $81.75   $81.80  
  Purchase #6 $189.50   5.412%   $199.7557   $199.76   $199.75   $199.80  
  Purchase #7 $194.64   4.156%   $202.7292   $202.73   $202.75   $202.70  
  7 purchase totals = $959.06       $1,024.2468   $1,024.25   $1,024.25   $1,024.30