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 $198.62   4.696%   $207.9472   $207.95   $207.95   $207.90  
  Purchase #2 $210.85   11.543%   $235.1884   $235.19   $235.20   $235.20  
  Purchase #3 $59.62   3.197%   $61.5261   $61.53   $61.55   $61.50  
  Purchase #4 $115.53   10.365%   $127.5047   $127.50   $127.50   $127.50  
  Purchase #5 $109.61   7.663%   $118.0094   $118.01   $118.00   $118.00  
  Purchase #6 $233.68   11.459%   $260.4574   $260.46   $260.45   $260.50  
  Purchase #7 $175.30   13.525%   $199.0093   $199.01   $199.00   $199.00  
  7 purchase totals = $1,103.21       $1,209.6425   $1,209.65   $1,209.65   $1,209.60