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 $41.93   4.372%   $43.7632   $43.76   $43.75   $43.80  
  Purchase #2 $148.42   3.161%   $153.1116   $153.11   $153.10   $153.10  
  Purchase #3 $64.45   13.500%   $73.1508   $73.15   $73.15   $73.20  
  Purchase #4 $79.32   3.476%   $82.0772   $82.08   $82.10   $82.10  
  Purchase #5 $183.71   6.326%   $195.3315   $195.33   $195.35   $195.30  
  Purchase #6 $163.80   6.373%   $174.239   $174.24   $174.25   $174.20  
  Purchase #7 $64.97   13.600%   $73.8059   $73.81   $73.80   $73.80  
  7 purchase totals = $746.60       $795.4792   $795.48   $795.50   $795.50