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 $63.92   9.495%   $69.9892   $69.99   $70.00   $70.00  
  Purchase #2 $128.28   13.849%   $146.0455   $146.05   $146.05   $146.00  
  Purchase #3 $178.66   8.787%   $194.3589   $194.36   $194.35   $194.40  
  Purchase #4 $48.36   9.408%   $52.9097   $52.91   $52.90   $52.90  
  Purchase #5 $232.91   6.495%   $248.0375   $248.04   $248.05   $248.00  
  Purchase #6 $221.48   8.126%   $239.4775   $239.48   $239.50   $239.50  
  Purchase #7 $168.30   9.241%   $183.8526   $183.85   $183.85   $183.90  
  7 purchase totals = $1,041.91       $1,134.6709   $1,134.68   $1,134.70   $1,134.70