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 $183.56   5.707%   $194.0358   $194.04   $194.05   $194.00  
  Purchase #2 $77.76   6.619%   $82.9069   $82.91   $82.90   $82.90  
  Purchase #3 $205.98   8.496%   $223.4801   $223.48   $223.50   $223.50  
  Purchase #4 $236.84   5.241%   $249.2528   $249.25   $249.25   $249.30  
  Purchase #5 $10.39   6.750%   $11.0913   $11.09   $11.10   $11.10  
  Purchase #6 $176.87   8.244%   $191.4512   $191.45   $191.45   $191.50  
  Purchase #7 $141.35   5.354%   $148.9179   $148.92   $148.90   $148.90  
  7 purchase totals = $1,032.75       $1,101.1360   $1,101.14   $1,101.15   $1,101.20