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 $62.96   6.472%   $67.0348   $67.03   $67.05   $67.00  
  Purchase #2 $26.91   8.397%   $29.1696   $29.17   $29.15   $29.20  
  Purchase #3 $84.79   12.564%   $95.443   $95.44   $95.45   $95.40  
  Purchase #4 $50.91   3.708%   $52.7977   $52.80   $52.80   $52.80  
  Purchase #5 $170.80   4.296%   $178.1376   $178.14   $178.15   $178.10  
  Purchase #6 $231.68   5.121%   $243.5443   $243.54   $243.55   $243.50  
  Purchase #7 $83.40   3.830%   $86.5942   $86.59   $86.60   $86.60  
  7 purchase totals = $711.45       $752.7212   $752.71   $752.75   $752.60