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 $33.60   6.432%   $35.7612   $35.76   $35.75   $35.80  
  Purchase #2 $72.97   4.306%   $76.1121   $76.11   $76.10   $76.10  
  Purchase #3 $201.56   7.847%   $217.3764   $217.38   $217.40   $217.40  
  Purchase #4 $68.52   12.268%   $76.926   $76.93   $76.95   $76.90  
  Purchase #5 $203.58   4.759%   $213.2684   $213.27   $213.25   $213.30  
  Purchase #6 $214.51   5.539%   $226.3917   $226.39   $226.40   $226.40  
  Purchase #7 $194.85   4.571%   $203.7566   $203.76   $203.75   $203.80  
  7 purchase totals = $989.59       $1,049.5924   $1,049.60   $1,049.60   $1,049.70