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 $161.56   9.366%   $176.6917   $176.69   $176.70   $176.70  
  Purchase #2 $69.72   10.472%   $77.0211   $77.02   $77.00   $77.00  
  Purchase #3 $43.61   9.114%   $47.5846   $47.58   $47.60   $47.60  
  Purchase #4 $106.97   10.799%   $118.5217   $118.52   $118.50   $118.50  
  Purchase #5 $100.47   7.482%   $107.9872   $107.99   $108.00   $108.00  
  Purchase #6 $137.47   3.769%   $142.6512   $142.65   $142.65   $142.70  
  Purchase #7 $173.64   13.158%   $196.4876   $196.49   $196.50   $196.50  
  7 purchase totals = $793.44       $866.9451   $866.94   $866.95   $867.00