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 $60.77   3.595%   $62.9547   $62.95   $62.95   $63.00  
  Purchase #2 $150.54   6.678%   $160.5931   $160.59   $160.60   $160.60  
  Purchase #3 $154.58   3.817%   $160.4803   $160.48   $160.50   $160.50  
  Purchase #4 $101.35   5.818%   $107.2465   $107.25   $107.25   $107.20  
  Purchase #5 $145.55   8.580%   $158.0382   $158.04   $158.05   $158.00  
  Purchase #6 $151.55   9.429%   $165.8396   $165.84   $165.85   $165.80  
  Purchase #7 $120.74   10.737%   $133.7039   $133.70   $133.70   $133.70  
  7 purchase totals = $885.08       $948.8563   $948.85   $948.90   $948.80