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 $57.99   7.280%   $62.2117   $62.21   $62.20   $62.20  
  Purchase #2 $219.90   13.209%   $248.9466   $248.95   $248.95   $248.90  
  Purchase #3 $194.26   7.486%   $208.8023   $208.80   $208.80   $208.80  
  Purchase #4 $204.76   5.630%   $216.288   $216.29   $216.30   $216.30  
  Purchase #5 $139.51   8.186%   $150.9303   $150.93   $150.95   $150.90  
  Purchase #6 $112.89   13.802%   $128.4711   $128.47   $128.45   $128.50  
  Purchase #7 $86.64   6.403%   $92.1876   $92.19   $92.20   $92.20  
  7 purchase totals = $1,015.95       $1,107.8376   $1,107.84   $1,107.85   $1,107.80