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 $69.68   5.535%   $73.5368   $73.54   $73.55   $73.50  
  Purchase #2 $6.87   4.294%   $7.165   $7.17   $7.15   $7.20  
  Purchase #3 $112.58   5.406%   $118.6661   $118.67   $118.65   $118.70  
  Purchase #4 $57.88   7.522%   $62.2337   $62.23   $62.25   $62.20  
  Purchase #5 $226.64   6.713%   $241.8543   $241.85   $241.85   $241.90  
  Purchase #6 $59.29   5.688%   $62.6624   $62.66   $62.65   $62.70  
  Purchase #7 $94.81   12.173%   $106.3512   $106.35   $106.35   $106.40  
  7 purchase totals = $627.75       $672.4695   $672.47   $672.45   $672.60