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 $63.78   13.717%   $72.5287   $72.53   $72.55   $72.50  
  Purchase #2 $132.84   9.173%   $145.0254   $145.03   $145.05   $145.00  
  Purchase #3 $11.25   5.352%   $11.8521   $11.85   $11.85   $11.90  
  Purchase #4 $148.81   3.393%   $153.8591   $153.86   $153.85   $153.90  
  Purchase #5 $222.67   13.243%   $252.1582   $252.16   $252.15   $252.20  
  Purchase #6 $205.25   3.847%   $213.146   $213.15   $213.15   $213.10  
  Purchase #7 $151.35   6.832%   $161.6902   $161.69   $161.70   $161.70  
  7 purchase totals = $935.95       $1,010.2597   $1,010.27   $1,010.30   $1,010.30