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 $148.33   5.333%   $156.2404   $156.24   $156.25   $156.20  
  Purchase #2 $93.83   7.265%   $100.6467   $100.65   $100.65   $100.60  
  Purchase #3 $167.54   4.772%   $175.535   $175.54   $175.55   $175.50  
  Purchase #4 $248.98   3.332%   $257.276   $257.28   $257.30   $257.30  
  Purchase #5 $122.49   9.661%   $134.3238   $134.32   $134.30   $134.30  
  Purchase #6 $193.36   13.604%   $219.6647   $219.66   $219.65   $219.70  
  Purchase #7 $60.31   3.458%   $62.3955   $62.40   $62.40   $62.40  
  7 purchase totals = $1,034.84       $1,106.0821   $1,106.09   $1,106.10   $1,106.00