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 $65.29   3.489%   $67.568   $67.57   $67.55   $67.60  
  Purchase #2 $164.75   3.710%   $170.8622   $170.86   $170.85   $170.90  
  Purchase #3 $199.75   4.612%   $208.9625   $208.96   $208.95   $209.00  
  Purchase #4 $23.53   7.813%   $25.3684   $25.37   $25.35   $25.40  
  Purchase #5 $186.83   8.529%   $202.7647   $202.76   $202.75   $202.80  
  Purchase #6 $41.84   5.661%   $44.2086   $44.21   $44.20   $44.20  
  Purchase #7 $45.83   3.193%   $47.2934   $47.29   $47.30   $47.30  
  7 purchase totals = $727.82       $767.0278   $767.02   $766.95   $767.20