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 $183.57   12.192%   $205.9509   $205.95   $205.95   $206.00  
  Purchase #2 $212.59   7.545%   $228.6299   $228.63   $228.65   $228.60  
  Purchase #3 $245.75   4.356%   $256.4549   $256.45   $256.45   $256.50  
  Purchase #4 $88.76   3.287%   $91.6775   $91.68   $91.70   $91.70  
  Purchase #5 $181.37   7.364%   $194.7261   $194.73   $194.75   $194.70  
  Purchase #6 $242.50   3.320%   $250.551   $250.55   $250.55   $250.60  
  Purchase #7 $217.54   7.188%   $233.1768   $233.18   $233.20   $233.20  
  7 purchase totals = $1,372.08       $1,461.1671   $1,461.17   $1,461.25   $1,461.30