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 $194.85   5.820%   $206.1903   $206.19   $206.20   $206.20  
  Purchase #2 $161.38   12.371%   $181.3443   $181.34   $181.35   $181.30  
  Purchase #3 $148.46   7.855%   $160.1215   $160.12   $160.10   $160.10  
  Purchase #4 $183.40   5.594%   $193.6594   $193.66   $193.65   $193.70  
  Purchase #5 $66.61   9.469%   $72.9173   $72.92   $72.90   $72.90  
  Purchase #6 $102.49   3.475%   $106.0515   $106.05   $106.05   $106.10  
  Purchase #7 $178.74   9.668%   $196.0206   $196.02   $196.00   $196.00  
  7 purchase totals = $1,035.93       $1,116.3049   $1,116.30   $1,116.25   $1,116.30