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 $43.69   3.568%   $45.2489   $45.25   $45.25   $45.20  
  Purchase #2 $179.93   12.236%   $201.9462   $201.95   $201.95   $201.90  
  Purchase #3 $150.88   3.706%   $156.4716   $156.47   $156.45   $156.50  
  Purchase #4 $245.90   6.650%   $262.2524   $262.25   $262.25   $262.30  
  Purchase #5 $45.95   5.311%   $48.3904   $48.39   $48.40   $48.40  
  Purchase #6 $173.94   4.303%   $181.4246   $181.42   $181.40   $181.40  
  Purchase #7 $165.90   7.692%   $178.661   $178.66   $178.65   $178.70  
  7 purchase totals = $1,006.19       $1,074.3951   $1,074.39   $1,074.35   $1,074.40