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 $69.33   5.296%   $73.0017   $73.00   $73.00   $73.00  
  Purchase #2 $88.97   5.693%   $94.0351   $94.04   $94.05   $94.00  
  Purchase #3 $220.42   12.432%   $247.8226   $247.82   $247.80   $247.80  
  Purchase #4 $172.80   12.221%   $193.9179   $193.92   $193.90   $193.90  
  Purchase #5 $233.83   3.279%   $241.4973   $241.50   $241.50   $241.50  
  Purchase #6 $124.28   13.676%   $141.2765   $141.28   $141.30   $141.30  
  Purchase #7 $37.77   9.798%   $41.4707   $41.47   $41.45   $41.50  
  7 purchase totals = $947.40       $1,033.0218   $1,033.03   $1,033.00   $1,033.00