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 $114.51   9.427%   $125.3049   $125.30   $125.30   $125.30  
  Purchase #2 $48.93   9.167%   $53.4154   $53.42   $53.40   $53.40  
  Purchase #3 $25.31   13.702%   $28.778   $28.78   $28.80   $28.80  
  Purchase #4 $207.58   7.120%   $222.3597   $222.36   $222.35   $222.40  
  Purchase #5 $186.65   8.544%   $202.5974   $202.60   $202.60   $202.60  
  Purchase #6 $147.38   4.173%   $153.5302   $153.53   $153.55   $153.50  
  Purchase #7 $221.30   4.607%   $231.4953   $231.50   $231.50   $231.50  
  7 purchase totals = $951.66       $1,017.4809   $1,017.49   $1,017.50   $1,017.50