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 $76.44   12.106%   $85.6938   $85.69   $85.70   $85.70  
  Purchase #2 $102.54   5.667%   $108.3509   $108.35   $108.35   $108.40  
  Purchase #3 $49.46   11.249%   $55.0238   $55.02   $55.00   $55.00  
  Purchase #4 $107.52   4.177%   $112.0111   $112.01   $112.00   $112.00  
  Purchase #5 $202.91   6.469%   $216.0362   $216.04   $216.05   $216.00  
  Purchase #6 $172.79   12.840%   $194.9762   $194.98   $195.00   $195.00  
  Purchase #7 $138.38   6.859%   $147.8715   $147.87   $147.85   $147.90  
  7 purchase totals = $850.04       $919.9635   $919.96   $919.95   $920.00