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 $191.56   5.447%   $201.9943   $201.99   $202.00   $202.00  
  Purchase #2 $211.78   13.305%   $239.9573   $239.96   $239.95   $240.00  
  Purchase #3 $184.38   12.623%   $207.6543   $207.65   $207.65   $207.70  
  Purchase #4 $236.96   7.256%   $254.1538   $254.15   $254.15   $254.20  
  Purchase #5 $81.83   4.835%   $85.7865   $85.79   $85.80   $85.80  
  Purchase #6 $178.65   6.720%   $190.6553   $190.66   $190.65   $190.70  
  Purchase #7 $170.95   6.130%   $181.4292   $181.43   $181.45   $181.40  
  7 purchase totals = $1,256.11       $1,361.6307   $1,361.63   $1,361.65   $1,361.80