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 $61.83   12.318%   $69.4462   $69.45   $69.45   $69.40  
  Purchase #2 $175.84   5.793%   $186.0264   $186.03   $186.05   $186.00  
  Purchase #3 $210.60   7.192%   $225.7464   $225.75   $225.75   $225.70  
  Purchase #4 $211.58   6.141%   $224.5731   $224.57   $224.55   $224.60  
  Purchase #5 $151.50   5.802%   $160.29   $160.29   $160.30   $160.30  
  Purchase #6 $126.82   3.189%   $130.8643   $130.86   $130.85   $130.90  
  Purchase #7 $187.97   5.579%   $198.4568   $198.46   $198.45   $198.50  
  7 purchase totals = $1,126.14       $1,195.4032   $1,195.41   $1,195.40   $1,195.40