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 $63.33   11.712%   $70.7472   $70.75   $70.75   $70.70  
  Purchase #2 $224.93   7.177%   $241.0732   $241.07   $241.05   $241.10  
  Purchase #3 $10.59   4.600%   $11.0771   $11.08   $11.10   $11.10  
  Purchase #4 $198.76   13.551%   $225.694   $225.69   $225.70   $225.70  
  Purchase #5 $221.25   6.325%   $235.2441   $235.24   $235.25   $235.20  
  Purchase #6 $109.39   13.234%   $123.8667   $123.87   $123.85   $123.90  
  Purchase #7 $217.28   13.674%   $246.9909   $246.99   $247.00   $247.00  
  7 purchase totals = $1,045.53       $1,154.6932   $1,154.69   $1,154.70   $1,154.70