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 $147.85   4.414%   $154.3761   $154.38   $154.40   $154.40  
  Purchase #2 $74.49   4.363%   $77.74   $77.74   $77.75   $77.70  
  Purchase #3 $167.35   11.554%   $186.6856   $186.69   $186.70   $186.70  
  Purchase #4 $106.29   13.330%   $120.4585   $120.46   $120.45   $120.50  
  Purchase #5 $164.71   6.230%   $174.9714   $174.97   $174.95   $175.00  
  Purchase #6 $216.84   8.716%   $235.7398   $235.74   $235.75   $235.70  
  Purchase #7 $72.76   4.469%   $76.0116   $76.01   $76.00   $76.00  
  7 purchase totals = $950.29       $1,025.9830   $1,025.99   $1,026.00   $1,026.00