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 $91.25   3.568%   $94.5058   $94.51   $94.50   $94.50  
  Purchase #2 $196.67   8.458%   $213.3043   $213.30   $213.30   $213.30  
  Purchase #3 $233.73   6.833%   $249.7008   $249.70   $249.70   $249.70  
  Purchase #4 $37.69   8.839%   $41.0214   $41.02   $41.00   $41.00  
  Purchase #5 $139.67   9.821%   $153.387   $153.39   $153.40   $153.40  
  Purchase #6 $74.75   8.188%   $80.8705   $80.87   $80.85   $80.90  
  Purchase #7 $215.98   11.805%   $241.4764   $241.48   $241.50   $241.50  
  7 purchase totals = $989.74       $1,074.2662   $1,074.27   $1,074.25   $1,074.30