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 $185.77   11.221%   $206.6153   $206.62   $206.60   $206.60  
  Purchase #2 $233.82   12.299%   $262.5775   $262.58   $262.60   $262.60  
  Purchase #3 $20.39   4.378%   $21.2827   $21.28   $21.30   $21.30  
  Purchase #4 $49.98   5.417%   $52.6874   $52.69   $52.70   $52.70  
  Purchase #5 $185.99   7.159%   $199.305   $199.31   $199.30   $199.30  
  Purchase #6 $106.66   13.341%   $120.8895   $120.89   $120.90   $120.90  
  Purchase #7 $29.77   6.829%   $31.803   $31.80   $31.80   $31.80  
  7 purchase totals = $812.38       $895.1604   $895.17   $895.20   $895.20