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 $56.76   11.417%   $63.2403   $63.24   $63.25   $63.20  
  Purchase #2 $219.71   8.181%   $237.6845   $237.68   $237.70   $237.70  
  Purchase #3 $8.25   4.474%   $8.6191   $8.62   $8.60   $8.60  
  Purchase #4 $170.80   4.292%   $178.1307   $178.13   $178.15   $178.10  
  Purchase #5 $191.86   4.624%   $200.7316   $200.73   $200.75   $200.70  
  Purchase #6 $148.28   9.436%   $162.2717   $162.27   $162.25   $162.30  
  Purchase #7 $226.49   3.781%   $235.0536   $235.05   $235.05   $235.10  
  7 purchase totals = $1,022.15       $1,085.7315   $1,085.72   $1,085.75   $1,085.70