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 $116.57   5.384%   $122.8461   $122.85   $122.85   $122.80  
  Purchase #2 $41.54   6.759%   $44.3477   $44.35   $44.35   $44.30  
  Purchase #3 $250.25   9.205%   $273.2855   $273.29   $273.30   $273.30  
  Purchase #4 $179.38   5.299%   $188.8853   $188.89   $188.90   $188.90  
  Purchase #5 $206.84   13.214%   $234.1718   $234.17   $234.15   $234.20  
  Purchase #6 $54.84   11.179%   $60.9706   $60.97   $60.95   $61.00  
  Purchase #7 $173.99   8.431%   $188.6591   $188.66   $188.65   $188.70  
  7 purchase totals = $1,023.41       $1,113.1661   $1,113.18   $1,113.15   $1,113.20