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 $55.56   12.720%   $62.6272   $62.63   $62.65   $62.60  
  Purchase #2 $205.68   3.270%   $212.4057   $212.41   $212.40   $212.40  
  Purchase #3 $56.98   10.852%   $63.1635   $63.16   $63.15   $63.20  
  Purchase #4 $134.74   11.553%   $150.3065   $150.31   $150.30   $150.30  
  Purchase #5 $126.33   7.188%   $135.4106   $135.41   $135.40   $135.40  
  Purchase #6 $215.46   7.331%   $231.2554   $231.26   $231.25   $231.30  
  Purchase #7 $170.27   5.606%   $179.8153   $179.82   $179.80   $179.80  
  7 purchase totals = $965.02       $1,034.9842   $1,035.00   $1,034.95   $1,035.00