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 $207.95   4.623%   $217.5635   $217.56   $217.55   $217.60  
  Purchase #2 $92.51   4.623%   $96.7867   $96.79   $96.80   $96.80  
  Purchase #3 $119.97   4.265%   $125.0867   $125.09   $125.10   $125.10  
  Purchase #4 $207.89   4.109%   $216.4322   $216.43   $216.45   $216.40  
  Purchase #5 $230.59   7.670%   $248.2763   $248.28   $248.30   $248.30  
  Purchase #6 $209.54   11.221%   $233.0525   $233.05   $233.05   $233.10  
  Purchase #7 $61.84   5.119%   $65.0056   $65.01   $65.00   $65.00  
  7 purchase totals = $1,130.29       $1,202.2035   $1,202.21   $1,202.25   $1,202.30