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 $178.86   8.522%   $194.1024   $194.10   $194.10   $194.10  
  Purchase #2 $193.45   8.648%   $210.1796   $210.18   $210.20   $210.20  
  Purchase #3 $119.40   4.834%   $125.1718   $125.17   $125.15   $125.20  
  Purchase #4 $242.68   11.441%   $270.445   $270.45   $270.45   $270.40  
  Purchase #5 $201.68   12.659%   $227.2107   $227.21   $227.20   $227.20  
  Purchase #6 $117.90   6.410%   $125.4574   $125.46   $125.45   $125.50  
  Purchase #7 $200.95   7.702%   $216.4272   $216.43   $216.45   $216.40  
  7 purchase totals = $1,254.92       $1,368.9941   $1,369.00   $1,369.00   $1,369.00