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 $60.48   6.250%   $64.26   $64.26   $64.25   $64.30  
  Purchase #2 $196.32   12.462%   $220.7854   $220.79   $220.80   $220.80  
  Purchase #3 $64.25   4.582%   $67.1939   $67.19   $67.20   $67.20  
  Purchase #4 $232.81   9.338%   $254.5498   $254.55   $254.55   $254.50  
  Purchase #5 $148.25   5.469%   $156.3578   $156.36   $156.35   $156.40  
  Purchase #6 $135.39   7.594%   $145.6715   $145.67   $145.65   $145.70  
  Purchase #7 $118.46   7.153%   $126.9334   $126.93   $126.95   $126.90  
  7 purchase totals = $955.96       $1,035.7518   $1,035.75   $1,035.75   $1,035.80