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 $205.82   5.771%   $217.6979   $217.70   $217.70   $217.70  
  Purchase #2 $247.44   3.781%   $256.7957   $256.80   $256.80   $256.80  
  Purchase #3 $225.80   10.118%   $248.6464   $248.65   $248.65   $248.60  
  Purchase #4 $101.49   6.506%   $108.0929   $108.09   $108.10   $108.10  
  Purchase #5 $74.79   11.500%   $83.3909   $83.39   $83.40   $83.40  
  Purchase #6 $10.77   8.840%   $11.7221   $11.72   $11.70   $11.70  
  Purchase #7 $73.85   11.458%   $82.3117   $82.31   $82.30   $82.30  
  7 purchase totals = $939.96       $1,008.6576   $1,008.66   $1,008.65   $1,008.60