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 $137.41   11.439%   $153.1283   $153.13   $153.15   $153.10  
  Purchase #2 $207.86   3.127%   $214.3598   $214.36   $214.35   $214.40  
  Purchase #3 $138.40   10.120%   $152.4061   $152.41   $152.40   $152.40  
  Purchase #4 $34.29   11.592%   $38.2649   $38.26   $38.25   $38.30  
  Purchase #5 $214.26   7.125%   $229.526   $229.53   $229.55   $229.50  
  Purchase #6 $181.46   3.220%   $187.303   $187.30   $187.30   $187.30  
  Purchase #7 $190.66   13.825%   $217.0187   $217.02   $217.00   $217.00  
  7 purchase totals = $1,104.34       $1,192.0068   $1,192.01   $1,192.00   $1,192.00