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 $118.58   6.576%   $126.3778   $126.38   $126.40   $126.40  
  Purchase #2 $186.57   4.854%   $195.6261   $195.63   $195.65   $195.60  
  Purchase #3 $155.95   5.368%   $164.3214   $164.32   $164.30   $164.30  
  Purchase #4 $102.30   6.501%   $108.9505   $108.95   $108.95   $109.00  
  Purchase #5 $208.51   6.288%   $221.6211   $221.62   $221.60   $221.60  
  Purchase #6 $147.35   8.264%   $159.527   $159.53   $159.55   $159.50  
  Purchase #7 $163.80   5.195%   $172.3094   $172.31   $172.30   $172.30  
  7 purchase totals = $1,083.06       $1,148.7333   $1,148.74   $1,148.75   $1,148.70