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 $62.55   6.325%   $66.5063   $66.51   $66.50   $66.50  
  Purchase #2 $168.63   6.511%   $179.6095   $179.61   $179.60   $179.60  
  Purchase #3 $156.65   12.381%   $176.0448   $176.04   $176.05   $176.00  
  Purchase #4 $45.48   8.124%   $49.1748   $49.17   $49.15   $49.20  
  Purchase #5 $198.64   4.635%   $207.847   $207.85   $207.85   $207.80  
  Purchase #6 $135.99   10.785%   $150.6565   $150.66   $150.65   $150.70  
  Purchase #7 $162.60   11.869%   $181.899   $181.90   $181.90   $181.90  
  7 purchase totals = $930.54       $1,011.7379   $1,011.74   $1,011.70   $1,011.70