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 $244.26   7.270%   $262.0177   $262.02   $262.00   $262.00  
  Purchase #2 $20.46   11.292%   $22.7703   $22.77   $22.75   $22.80  
  Purchase #3 $145.97   12.730%   $164.552   $164.55   $164.55   $164.60  
  Purchase #4 $212.69   6.747%   $227.0402   $227.04   $227.05   $227.00  
  Purchase #5 $52.48   3.607%   $54.373   $54.37   $54.35   $54.40  
  Purchase #6 $159.76   3.832%   $165.882   $165.88   $165.90   $165.90  
  Purchase #7 $197.50   8.294%   $213.8807   $213.88   $213.90   $213.90  
  7 purchase totals = $1,033.12       $1,110.5159   $1,110.51   $1,110.50   $1,110.60