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 $90.85   4.822%   $95.2308   $95.23   $95.25   $95.20  
  Purchase #2 $127.91   13.671%   $145.3966   $145.40   $145.40   $145.40  
  Purchase #3 $62.48   11.575%   $69.7121   $69.71   $69.70   $69.70  
  Purchase #4 $242.49   6.687%   $258.7053   $258.71   $258.70   $258.70  
  Purchase #5 $19.52   6.506%   $20.79   $20.79   $20.80   $20.80  
  Purchase #6 $80.54   4.278%   $83.9855   $83.99   $84.00   $84.00  
  Purchase #7 $20.99   13.636%   $23.8522   $23.85   $23.85   $23.90  
  7 purchase totals = $644.78       $697.6725   $697.68   $697.70   $697.70