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 $184.84   7.696%   $199.0653   $199.07   $199.05   $199.10  
  Purchase #2 $183.75   13.489%   $208.536   $208.54   $208.55   $208.50  
  Purchase #3 $186.39   7.797%   $200.9228   $200.92   $200.90   $200.90  
  Purchase #4 $29.74   10.651%   $32.9076   $32.91   $32.90   $32.90  
  Purchase #5 $65.92   3.835%   $68.448   $68.45   $68.45   $68.40  
  Purchase #6 $105.32   12.309%   $118.2838   $118.28   $118.30   $118.30  
  Purchase #7 $186.47   4.334%   $194.5516   $194.55   $194.55   $194.60  
  7 purchase totals = $942.43       $1,022.7151   $1,022.72   $1,022.70   $1,022.70