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 $92.90   5.325%   $97.8469   $97.85   $97.85   $97.80  
  Purchase #2 $108.89   3.735%   $112.957   $112.96   $112.95   $113.00  
  Purchase #3 $223.97   11.357%   $249.4063   $249.41   $249.40   $249.40  
  Purchase #4 $45.56   4.720%   $47.7104   $47.71   $47.70   $47.70  
  Purchase #5 $131.88   11.551%   $147.1135   $147.11   $147.10   $147.10  
  Purchase #6 $213.87   13.604%   $242.9649   $242.96   $242.95   $243.00  
  Purchase #7 $107.98   4.843%   $113.2095   $113.21   $113.20   $113.20  
  7 purchase totals = $925.05       $1,011.2085   $1,011.21   $1,011.15   $1,011.20