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 $58.62   7.649%   $63.1038   $63.10   $63.10   $63.10  
  Purchase #2 $176.50   6.323%   $187.6601   $187.66   $187.65   $187.70  
  Purchase #3 $245.74   6.833%   $262.5314   $262.53   $262.55   $262.50  
  Purchase #4 $211.29   7.676%   $227.5086   $227.51   $227.50   $227.50  
  Purchase #5 $59.76   6.186%   $63.4568   $63.46   $63.45   $63.50  
  Purchase #6 $155.46   13.586%   $176.5808   $176.58   $176.60   $176.60  
  Purchase #7 $210.67   8.645%   $228.8824   $228.88   $228.90   $228.90  
  7 purchase totals = $1,118.04       $1,209.7239   $1,209.72   $1,209.75   $1,209.80