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 $184.55   7.127%   $197.7029   $197.70   $197.70   $197.70  
  Purchase #2 $154.97   13.526%   $175.9312   $175.93   $175.95   $175.90  
  Purchase #3 $102.82   11.711%   $114.8613   $114.86   $114.85   $114.90  
  Purchase #4 $126.40   3.105%   $130.3247   $130.32   $130.30   $130.30  
  Purchase #5 $194.85   7.492%   $209.4482   $209.45   $209.45   $209.40  
  Purchase #6 $30.77   7.759%   $33.1574   $33.16   $33.15   $33.20  
  Purchase #7 $162.36   6.294%   $172.5789   $172.58   $172.60   $172.60  
  7 purchase totals = $956.72       $1,034.0046   $1,034.00   $1,034.00   $1,034.00