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 $195.86   10.616%   $216.6525   $216.65   $216.65   $216.70  
  Purchase #2 $41.47   4.421%   $43.3034   $43.30   $43.30   $43.30  
  Purchase #3 $23.93   7.405%   $25.702   $25.70   $25.70   $25.70  
  Purchase #4 $52.56   9.616%   $57.6142   $57.61   $57.60   $57.60  
  Purchase #5 $211.95   13.593%   $240.7604   $240.76   $240.75   $240.80  
  Purchase #6 $116.28   8.623%   $126.3068   $126.31   $126.30   $126.30  
  Purchase #7 $114.98   9.868%   $126.3262   $126.33   $126.35   $126.30  
  7 purchase totals = $757.03       $836.6655   $836.66   $836.65   $836.70