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 $85.88   7.446%   $92.2746   $92.27   $92.25   $92.30  
  Purchase #2 $177.63   10.171%   $195.6967   $195.70   $195.70   $195.70  
  Purchase #3 $59.79   4.168%   $62.282   $62.28   $62.30   $62.30  
  Purchase #4 $162.99   12.499%   $183.3621   $183.36   $183.35   $183.40  
  Purchase #5 $189.65   4.551%   $198.281   $198.28   $198.30   $198.30  
  Purchase #6 $107.35   6.351%   $114.1678   $114.17   $114.15   $114.20  
  Purchase #7 $140.52   8.598%   $152.6019   $152.60   $152.60   $152.60  
  7 purchase totals = $923.81       $998.6661   $998.66   $998.65   $998.80