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 $185.29   8.617%   $201.2564   $201.26   $201.25   $201.30  
  Purchase #2 $36.54   7.400%   $39.244   $39.24   $39.25   $39.20  
  Purchase #3 $248.45   10.465%   $274.4503   $274.45   $274.45   $274.50  
  Purchase #4 $82.32   3.585%   $85.2712   $85.27   $85.25   $85.30  
  Purchase #5 $95.49   10.620%   $105.631   $105.63   $105.65   $105.60  
  Purchase #6 $148.25   9.827%   $162.8185   $162.82   $162.80   $162.80  
  Purchase #7 $175.36   11.450%   $195.4387   $195.44   $195.45   $195.40  
  7 purchase totals = $971.70       $1,064.1101   $1,064.11   $1,064.10   $1,064.10