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 $53.97   9.209%   $58.9401   $58.94   $58.95   $58.90  
  Purchase #2 $208.86   11.390%   $232.6492   $232.65   $232.65   $232.60  
  Purchase #3 $250.29   13.323%   $283.6361   $283.64   $283.65   $283.60  
  Purchase #4 $93.47   9.277%   $102.1412   $102.14   $102.15   $102.10  
  Purchase #5 $191.99   12.733%   $216.4361   $216.44   $216.45   $216.40  
  Purchase #6 $165.91   3.749%   $172.13   $172.13   $172.15   $172.10  
  Purchase #7 $123.87   4.328%   $129.2311   $129.23   $129.25   $129.20  
  7 purchase totals = $1,088.36       $1,195.1638   $1,195.17   $1,195.25   $1,194.90