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 $60.83   10.130%   $66.9921   $66.99   $67.00   $67.00  
  Purchase #2 $169.63   8.233%   $183.5956   $183.60   $183.60   $183.60  
  Purchase #3 $159.60   7.420%   $171.4423   $171.44   $171.45   $171.40  
  Purchase #4 $219.33   11.200%   $243.895   $243.90   $243.90   $243.90  
  Purchase #5 $141.28   5.798%   $149.4714   $149.47   $149.45   $149.50  
  Purchase #6 $223.31   7.628%   $240.3441   $240.34   $240.35   $240.30  
  Purchase #7 $175.90   3.367%   $181.8226   $181.82   $181.80   $181.80  
  7 purchase totals = $1,149.88       $1,237.5631   $1,237.56   $1,237.55   $1,237.50