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 $88.90   9.120%   $97.0077   $97.01   $97.00   $97.00  
  Purchase #2 $93.51   11.573%   $104.3319   $104.33   $104.35   $104.30  
  Purchase #3 $218.26   7.575%   $234.7932   $234.79   $234.80   $234.80  
  Purchase #4 $166.36   13.108%   $188.1665   $188.17   $188.15   $188.20  
  Purchase #5 $93.69   12.721%   $105.6083   $105.61   $105.60   $105.60  
  Purchase #6 $130.70   7.794%   $140.8868   $140.89   $140.90   $140.90  
  Purchase #7 $223.58   4.757%   $234.2157   $234.22   $234.20   $234.20  
  7 purchase totals = $1,015.00       $1,105.0101   $1,105.02   $1,105.00   $1,105.00