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 $180.36   11.431%   $200.977   $200.98   $201.00   $201.00  
  Purchase #2 $74.41   3.609%   $77.0955   $77.10   $77.10   $77.10  
  Purchase #3 $61.55   3.292%   $63.5762   $63.58   $63.60   $63.60  
  Purchase #4 $66.79   5.157%   $70.2344   $70.23   $70.25   $70.20  
  Purchase #5 $66.77   13.451%   $75.7512   $75.75   $75.75   $75.80  
  Purchase #6 $143.37   9.393%   $156.8367   $156.84   $156.85   $156.80  
  Purchase #7 $112.79   8.790%   $122.7042   $122.70   $122.70   $122.70  
  7 purchase totals = $706.04       $767.1752   $767.18   $767.25   $767.20