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 $249.73   5.582%   $263.6699   $263.67   $263.65   $263.70  
  Purchase #2 $181.77   7.608%   $195.5991   $195.60   $195.60   $195.60  
  Purchase #3 $13.89   7.214%   $14.892   $14.89   $14.90   $14.90  
  Purchase #4 $190.69   13.760%   $216.9289   $216.93   $216.95   $216.90  
  Purchase #5 $228.57   3.107%   $235.6717   $235.67   $235.65   $235.70  
  Purchase #6 $119.33   9.376%   $130.5184   $130.52   $130.50   $130.50  
  Purchase #7 $64.36   8.482%   $69.819   $69.82   $69.80   $69.80  
  7 purchase totals = $1,048.34       $1,127.0990   $1,127.10   $1,127.05   $1,127.10