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 $71.41   5.861%   $75.5953   $75.60   $75.60   $75.60  
  Purchase #2 $212.63   12.775%   $239.7935   $239.79   $239.80   $239.80  
  Purchase #3 $6.49   7.466%   $6.9745   $6.97   $6.95   $7.00  
  Purchase #4 $57.60   7.456%   $61.8947   $61.89   $61.90   $61.90  
  Purchase #5 $193.31   4.573%   $202.1501   $202.15   $202.15   $202.20  
  Purchase #6 $219.51   9.675%   $240.7476   $240.75   $240.75   $240.70  
  Purchase #7 $183.76   8.515%   $199.4072   $199.41   $199.40   $199.40  
  7 purchase totals = $944.71       $1,026.5629   $1,026.56   $1,026.55   $1,026.60