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 $83.68   13.779%   $95.2103   $95.21   $95.20   $95.20  
  Purchase #2 $181.80   8.194%   $196.6967   $196.70   $196.70   $196.70  
  Purchase #3 $5.68   10.750%   $6.2906   $6.29   $6.30   $6.30  
  Purchase #4 $31.65   3.807%   $32.8549   $32.85   $32.85   $32.90  
  Purchase #5 $154.56   7.102%   $165.5369   $165.54   $165.55   $165.50  
  Purchase #6 $157.31   10.501%   $173.8291   $173.83   $173.85   $173.80  
  Purchase #7 $62.29   12.133%   $69.8476   $69.85   $69.85   $69.80  
  7 purchase totals = $676.97       $740.2661   $740.27   $740.30   $740.20