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 $67.88   4.799%   $71.1376   $71.14   $71.15   $71.10  
  Purchase #2 $205.78   5.137%   $216.3509   $216.35   $216.35   $216.40  
  Purchase #3 $78.25   12.679%   $88.1713   $88.17   $88.15   $88.20  
  Purchase #4 $99.60   9.219%   $108.7821   $108.78   $108.80   $108.80  
  Purchase #5 $182.34   13.323%   $206.6332   $206.63   $206.65   $206.60  
  Purchase #6 $214.86   4.814%   $225.2034   $225.20   $225.20   $225.20  
  Purchase #7 $34.40   6.432%   $36.6126   $36.61   $36.60   $36.60  
  7 purchase totals = $883.11       $952.8911   $952.88   $952.90   $952.90