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 $173.97   10.692%   $192.5709   $192.57   $192.55   $192.60  
  Purchase #2 $114.40   9.613%   $125.3973   $125.40   $125.40   $125.40  
  Purchase #3 $202.76   10.364%   $223.774   $223.77   $223.75   $223.80  
  Purchase #4 $36.32   12.319%   $40.7943   $40.79   $40.80   $40.80  
  Purchase #5 $122.50   13.221%   $138.6957   $138.70   $138.70   $138.70  
  Purchase #6 $122.76   13.452%   $139.2737   $139.27   $139.25   $139.30  
  Purchase #7 $185.97   11.288%   $206.9623   $206.96   $206.95   $207.00  
  7 purchase totals = $958.68       $1,067.4682   $1,067.46   $1,067.40   $1,067.60