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 $147.62   4.737%   $154.6128   $154.61   $154.60   $154.60  
  Purchase #2 $175.81   9.170%   $191.9318   $191.93   $191.95   $191.90  
  Purchase #3 $160.67   10.551%   $177.6223   $177.62   $177.60   $177.60  
  Purchase #4 $241.90   10.810%   $268.0494   $268.05   $268.05   $268.00  
  Purchase #5 $212.60   4.829%   $222.8665   $222.87   $222.85   $222.90  
  Purchase #6 $242.71   5.328%   $255.6416   $255.64   $255.65   $255.60  
  Purchase #7 $182.51   12.776%   $205.8275   $205.83   $205.85   $205.80  
  7 purchase totals = $1,363.82       $1,476.5519   $1,476.55   $1,476.55   $1,476.40