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 $62.54   13.582%   $71.0342   $71.03   $71.05   $71.00  
  Purchase #2 $214.88   12.262%   $241.2286   $241.23   $241.25   $241.20  
  Purchase #3 $219.68   6.753%   $234.515   $234.52   $234.50   $234.50  
  Purchase #4 $123.60   5.739%   $130.6934   $130.69   $130.70   $130.70  
  Purchase #5 $232.60   12.362%   $261.354   $261.35   $261.35   $261.40  
  Purchase #6 $54.41   10.805%   $60.289   $60.29   $60.30   $60.30  
  Purchase #7 $210.62   7.593%   $226.6124   $226.61   $226.60   $226.60  
  7 purchase totals = $1,118.33       $1,225.7266   $1,225.72   $1,225.75   $1,225.70