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 $84.59   9.560%   $92.6768   $92.68   $92.70   $92.70  
  Purchase #2 $7.50   3.288%   $7.7466   $7.75   $7.75   $7.70  
  Purchase #3 $64.80   6.565%   $69.0541   $69.05   $69.05   $69.10  
  Purchase #4 $115.74   9.514%   $126.7515   $126.75   $126.75   $126.80  
  Purchase #5 $100.30   6.300%   $106.6189   $106.62   $106.60   $106.60  
  Purchase #6 $102.66   10.670%   $113.6138   $113.61   $113.60   $113.60  
  Purchase #7 $232.29   7.344%   $249.3494   $249.35   $249.35   $249.30  
  7 purchase totals = $707.88       $765.8111   $765.81   $765.80   $765.80