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 $68.39   9.458%   $74.8583   $74.86   $74.85   $74.90  
  Purchase #2 $212.30   10.864%   $235.3643   $235.36   $235.35   $235.40  
  Purchase #3 $177.77   7.763%   $191.5703   $191.57   $191.55   $191.60  
  Purchase #4 $170.67   13.296%   $193.3623   $193.36   $193.35   $193.40  
  Purchase #5 $183.49   7.855%   $197.9031   $197.90   $197.90   $197.90  
  Purchase #6 $240.66   3.690%   $249.5404   $249.54   $249.55   $249.50  
  Purchase #7 $120.34   3.860%   $124.9851   $124.99   $125.00   $125.00  
  7 purchase totals = $1,173.62       $1,267.5838   $1,267.58   $1,267.55   $1,267.70