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 $43.32   7.582%   $46.6045   $46.60   $46.60   $46.60  
  Purchase #2 $214.38   12.773%   $241.7628   $241.76   $241.75   $241.80  
  Purchase #3 $163.78   7.325%   $175.7769   $175.78   $175.80   $175.80  
  Purchase #4 $93.31   4.811%   $97.7991   $97.80   $97.80   $97.80  
  Purchase #5 $241.40   6.405%   $256.8617   $256.86   $256.85   $256.90  
  Purchase #6 $225.44   3.861%   $234.1442   $234.14   $234.15   $234.10  
  Purchase #7 $36.95   11.134%   $41.064   $41.06   $41.05   $41.10  
  7 purchase totals = $1,018.58       $1,094.0132   $1,094.00   $1,094.00   $1,094.10