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 $88.78   10.410%   $98.022   $98.02   $98.00   $98.00  
  Purchase #2 $82.43   13.527%   $93.5803   $93.58   $93.60   $93.60  
  Purchase #3 $22.87   5.478%   $24.1228   $24.12   $24.10   $24.10  
  Purchase #4 $226.63   12.194%   $254.2653   $254.27   $254.25   $254.30  
  Purchase #5 $52.38   3.323%   $54.1206   $54.12   $54.10   $54.10  
  Purchase #6 $64.27   3.664%   $66.6249   $66.62   $66.60   $66.60  
  Purchase #7 $133.68   7.150%   $143.2381   $143.24   $143.25   $143.20  
  7 purchase totals = $671.04       $733.9740   $733.97   $733.90   $733.90