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 $95.47   8.587%   $103.668   $103.67   $103.65   $103.70  
  Purchase #2 $223.75   8.658%   $243.1223   $243.12   $243.10   $243.10  
  Purchase #3 $149.58   7.798%   $161.2442   $161.24   $161.25   $161.20  
  Purchase #4 $13.26   7.860%   $14.3022   $14.30   $14.30   $14.30  
  Purchase #5 $45.96   5.443%   $48.4616   $48.46   $48.45   $48.50  
  Purchase #6 $250.64   13.552%   $284.6067   $284.61   $284.60   $284.60  
  Purchase #7 $213.80   12.166%   $239.8109   $239.81   $239.80   $239.80  
  7 purchase totals = $992.46       $1,095.2159   $1,095.21   $1,095.15   $1,095.20