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 $184.56   9.357%   $201.8293   $201.83   $201.85   $201.80  
  Purchase #2 $64.94   4.288%   $67.7246   $67.72   $67.70   $67.70  
  Purchase #3 $153.49   9.488%   $168.0531   $168.05   $168.05   $168.10  
  Purchase #4 $59.89   5.148%   $62.9731   $62.97   $62.95   $63.00  
  Purchase #5 $190.83   10.367%   $210.6133   $210.61   $210.60   $210.60  
  Purchase #6 $9.70   13.367%   $10.9966   $11.00   $11.00   $11.00  
  Purchase #7 $235.99   4.575%   $246.7865   $246.79   $246.80   $246.80  
  7 purchase totals = $899.40       $968.9765   $968.97   $968.95   $969.00