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 $182.60   7.284%   $195.9006   $195.90   $195.90   $195.90  
  Purchase #2 $164.57   4.383%   $171.7831   $171.78   $171.80   $171.80  
  Purchase #3 $137.66   3.394%   $142.3322   $142.33   $142.35   $142.30  
  Purchase #4 $71.60   8.841%   $77.9302   $77.93   $77.95   $77.90  
  Purchase #5 $79.25   11.561%   $88.4121   $88.41   $88.40   $88.40  
  Purchase #6 $107.77   4.814%   $112.958   $112.96   $112.95   $113.00  
  Purchase #7 $34.77   6.120%   $36.8979   $36.90   $36.90   $36.90  
  7 purchase totals = $778.22       $826.2141   $826.21   $826.25   $826.20