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 $139.26   9.354%   $152.2864   $152.29   $152.30   $152.30  
  Purchase #2 $56.44   7.645%   $60.7548   $60.75   $60.75   $60.80  
  Purchase #3 $61.32   6.401%   $65.2451   $65.25   $65.25   $65.20  
  Purchase #4 $114.48   12.485%   $128.7728   $128.77   $128.75   $128.80  
  Purchase #5 $161.70   12.360%   $181.6861   $181.69   $181.70   $181.70  
  Purchase #6 $113.33   5.841%   $119.9496   $119.95   $119.95   $119.90  
  Purchase #7 $48.61   10.400%   $53.6654   $53.67   $53.65   $53.70  
  7 purchase totals = $695.14       $762.3602   $762.37   $762.35   $762.40