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 $59.55   5.465%   $62.8044   $62.80   $62.80   $62.80  
  Purchase #2 $82.65   7.456%   $88.8124   $88.81   $88.80   $88.80  
  Purchase #3 $79.33   11.383%   $88.3601   $88.36   $88.35   $88.40  
  Purchase #4 $103.43   5.171%   $108.7784   $108.78   $108.80   $108.80  
  Purchase #5 $221.93   7.565%   $238.719   $238.72   $238.70   $238.70  
  Purchase #6 $110.40   3.260%   $113.999   $114.00   $114.00   $114.00  
  Purchase #7 $40.68   7.638%   $43.7871   $43.79   $43.80   $43.80  
  7 purchase totals = $697.97       $745.2604   $745.26   $745.25   $745.30