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 $177.60   9.262%   $194.0493   $194.05   $194.05   $194.00  
  Purchase #2 $108.82   5.560%   $114.8704   $114.87   $114.85   $114.90  
  Purchase #3 $32.51   12.178%   $36.4691   $36.47   $36.45   $36.50  
  Purchase #4 $196.37   7.312%   $210.7286   $210.73   $210.75   $210.70  
  Purchase #5 $54.51   4.262%   $56.8332   $56.83   $56.85   $56.80  
  Purchase #6 $33.97   7.549%   $36.5344   $36.53   $36.55   $36.50  
  Purchase #7 $109.75   4.656%   $114.86   $114.86   $114.85   $114.90  
  7 purchase totals = $713.53       $764.3450   $764.34   $764.35   $764.30