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 $91.50   11.420%   $101.9493   $101.95   $101.95   $101.90  
  Purchase #2 $247.87   11.206%   $275.6463   $275.65   $275.65   $275.60  
  Purchase #3 $177.63   11.636%   $198.299   $198.30   $198.30   $198.30  
  Purchase #4 $50.76   11.780%   $56.7395   $56.74   $56.75   $56.70  
  Purchase #5 $128.63   4.640%   $134.5984   $134.60   $134.60   $134.60  
  Purchase #6 $210.48   10.179%   $231.9048   $231.90   $231.90   $231.90  
  Purchase #7 $196.32   7.753%   $211.5407   $211.54   $211.55   $211.50  
  7 purchase totals = $1,103.19       $1,210.6780   $1,210.68   $1,210.70   $1,210.50