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 $60.89   5.113%   $64.0033   $64.00   $64.00   $64.00  
  Purchase #2 $163.49   10.596%   $180.8134   $180.81   $180.80   $180.80  
  Purchase #3 $195.84   8.289%   $212.0732   $212.07   $212.05   $212.10  
  Purchase #4 $127.32   10.804%   $141.0757   $141.08   $141.10   $141.10  
  Purchase #5 $219.66   8.731%   $238.8385   $238.84   $238.85   $238.80  
  Purchase #6 $161.56   4.336%   $168.5652   $168.57   $168.55   $168.60  
  Purchase #7 $195.83   6.504%   $208.5668   $208.57   $208.55   $208.60  
  7 purchase totals = $1,124.59       $1,213.9361   $1,213.94   $1,213.90   $1,214.00