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 $248.63   5.454%   $262.1903   $262.19   $262.20   $262.20  
  Purchase #2 $63.41   11.144%   $70.4764   $70.48   $70.50   $70.50  
  Purchase #3 $223.51   9.822%   $245.4632   $245.46   $245.45   $245.50  
  Purchase #4 $199.67   9.459%   $218.5568   $218.56   $218.55   $218.60  
  Purchase #5 $96.32   8.850%   $104.8443   $104.84   $104.85   $104.80  
  Purchase #6 $83.50   11.332%   $92.9622   $92.96   $92.95   $93.00  
  Purchase #7 $176.50   9.772%   $193.7476   $193.75   $193.75   $193.70  
  7 purchase totals = $1,091.54       $1,188.2408   $1,188.24   $1,188.25   $1,188.30