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 $222.66   5.119%   $234.058   $234.06   $234.05   $234.10  
  Purchase #2 $121.90   4.192%   $127.01   $127.01   $127.00   $127.00  
  Purchase #3 $21.63   10.454%   $23.8912   $23.89   $23.90   $23.90  
  Purchase #4 $171.56   11.211%   $190.7936   $190.79   $190.80   $190.80  
  Purchase #5 $193.26   13.602%   $219.5472   $219.55   $219.55   $219.50  
  Purchase #6 $225.46   8.430%   $244.4663   $244.47   $244.45   $244.50  
  Purchase #7 $113.62   5.533%   $119.9066   $119.91   $119.90   $119.90  
  7 purchase totals = $1,070.09       $1,159.6729   $1,159.68   $1,159.65   $1,159.70