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 $86.78   8.236%   $93.9272   $93.93   $93.95   $93.90  
  Purchase #2 $184.37   5.576%   $194.6505   $194.65   $194.65   $194.70  
  Purchase #3 $160.26   10.557%   $177.1786   $177.18   $177.20   $177.20  
  Purchase #4 $81.51   6.425%   $86.747   $86.75   $86.75   $86.70  
  Purchase #5 $114.30   10.342%   $126.1209   $126.12   $126.10   $126.10  
  Purchase #6 $198.37   4.747%   $207.7866   $207.79   $207.80   $207.80  
  Purchase #7 $107.99   11.605%   $120.5222   $120.52   $120.50   $120.50  
  7 purchase totals = $933.58       $1,006.9330   $1,006.94   $1,006.95   $1,006.90