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 $62.45   11.376%   $69.5543   $69.55   $69.55   $69.60  
  Purchase #2 $169.55   7.363%   $182.034   $182.03   $182.05   $182.00  
  Purchase #3 $163.30   5.150%   $171.71   $171.71   $171.70   $171.70  
  Purchase #4 $161.85   5.397%   $170.585   $170.59   $170.60   $170.60  
  Purchase #5 $31.86   12.160%   $35.7342   $35.73   $35.75   $35.70  
  Purchase #6 $111.53   7.267%   $119.6349   $119.63   $119.65   $119.60  
  Purchase #7 $95.54   13.551%   $108.4866   $108.49   $108.50   $108.50  
  7 purchase totals = $796.08       $857.7390   $857.73   $857.80   $857.70