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 $76.54   11.805%   $85.5755   $85.58   $85.60   $85.60  
  Purchase #2 $213.42   4.560%   $223.152   $223.15   $223.15   $223.20  
  Purchase #3 $193.87   13.822%   $220.6667   $220.67   $220.65   $220.70  
  Purchase #4 $146.26   10.440%   $161.5295   $161.53   $161.55   $161.50  
  Purchase #5 $54.90   3.264%   $56.6919   $56.69   $56.70   $56.70  
  Purchase #6 $116.31   3.209%   $120.0424   $120.04   $120.05   $120.00  
  Purchase #7 $80.65   3.853%   $83.7574   $83.76   $83.75   $83.80  
  7 purchase totals = $881.95       $951.4154   $951.42   $951.45   $951.50