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 $94.26   13.321%   $106.8164   $106.82   $106.80   $106.80  
  Purchase #2 $15.54   8.233%   $16.8194   $16.82   $16.80   $16.80  
  Purchase #3 $111.59   6.179%   $118.4851   $118.49   $118.50   $118.50  
  Purchase #4 $201.84   4.655%   $211.2357   $211.24   $211.25   $211.20  
  Purchase #5 $248.62   10.829%   $275.5431   $275.54   $275.55   $275.50  
  Purchase #6 $180.29   13.599%   $204.8076   $204.81   $204.80   $204.80  
  Purchase #7 $174.36   3.714%   $180.8357   $180.84   $180.85   $180.80  
  7 purchase totals = $1,026.50       $1,114.5430   $1,114.56   $1,114.55   $1,114.40