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 $244.35   7.387%   $262.4001   $262.40   $262.40   $262.40  
  Purchase #2 $157.30   9.597%   $172.3961   $172.40   $172.40   $172.40  
  Purchase #3 $125.93   3.717%   $130.6108   $130.61   $130.60   $130.60  
  Purchase #4 $185.52   6.729%   $198.0036   $198.00   $198.00   $198.00  
  Purchase #5 $134.65   4.318%   $140.4642   $140.46   $140.45   $140.50  
  Purchase #6 $86.39   12.163%   $96.8976   $96.90   $96.90   $96.90  
  Purchase #7 $24.53   5.691%   $25.926   $25.93   $25.95   $25.90  
  7 purchase totals = $958.67       $1,026.6984   $1,026.70   $1,026.70   $1,026.70