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 $146.88   10.504%   $162.3083   $162.31   $162.30   $162.30  
  Purchase #2 $168.92   13.278%   $191.3492   $191.35   $191.35   $191.30  
  Purchase #3 $25.48   3.502%   $26.3723   $26.37   $26.35   $26.40  
  Purchase #4 $178.78   8.748%   $194.4197   $194.42   $194.40   $194.40  
  Purchase #5 $45.56   10.837%   $50.4973   $50.50   $50.50   $50.50  
  Purchase #6 $192.77   10.830%   $213.647   $213.65   $213.65   $213.60  
  Purchase #7 $166.58   5.295%   $175.4004   $175.40   $175.40   $175.40  
  7 purchase totals = $924.97       $1,013.9942   $1,014.00   $1,013.95   $1,013.90