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 $98.61   8.458%   $106.9504   $106.95   $106.95   $107.00  
  Purchase #2 $7.56   5.182%   $7.9518   $7.95   $7.95   $8.00  
  Purchase #3 $131.55   8.581%   $142.8383   $142.84   $142.85   $142.80  
  Purchase #4 $155.81   8.449%   $168.9744   $168.97   $168.95   $169.00  
  Purchase #5 $168.62   9.107%   $183.9762   $183.98   $184.00   $184.00  
  Purchase #6 $136.28   6.254%   $144.803   $144.80   $144.80   $144.80  
  Purchase #7 $39.41   5.154%   $41.4412   $41.44   $41.45   $41.40  
  7 purchase totals = $737.84       $796.9353   $796.93   $796.95   $797.00