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 $175.76   11.482%   $195.9408   $195.94   $195.95   $195.90  
  Purchase #2 $70.52   5.498%   $74.3972   $74.40   $74.40   $74.40  
  Purchase #3 $200.77   8.331%   $217.4961   $217.50   $217.50   $217.50  
  Purchase #4 $231.55   13.144%   $261.9849   $261.98   $262.00   $262.00  
  Purchase #5 $166.87   10.379%   $184.1894   $184.19   $184.20   $184.20  
  Purchase #6 $59.95   12.562%   $67.4809   $67.48   $67.50   $67.50  
  Purchase #7 $115.32   10.536%   $127.4701   $127.47   $127.45   $127.50  
  7 purchase totals = $1,020.74       $1,128.9594   $1,128.96   $1,129.00   $1,129.00