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 $60.42   11.666%   $67.4686   $67.47   $67.45   $67.50  
  Purchase #2 $172.85   12.569%   $194.5755   $194.58   $194.60   $194.60  
  Purchase #3 $217.70   13.773%   $247.6838   $247.68   $247.70   $247.70  
  Purchase #4 $144.45   11.307%   $160.783   $160.78   $160.80   $160.80  
  Purchase #5 $192.49   12.261%   $216.0912   $216.09   $216.10   $216.10  
  Purchase #6 $241.86   9.176%   $264.0531   $264.05   $264.05   $264.10  
  Purchase #7 $17.87   4.565%   $18.6858   $18.69   $18.70   $18.70  
  7 purchase totals = $1,047.64       $1,169.3410   $1,169.34   $1,169.40   $1,169.50