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 $94.62   5.206%   $99.5459   $99.55   $99.55   $99.50  
  Purchase #2 $140.67   7.496%   $151.2146   $151.21   $151.20   $151.20  
  Purchase #3 $179.44   6.537%   $191.17   $191.17   $191.15   $191.20  
  Purchase #4 $11.38   5.851%   $12.0458   $12.05   $12.05   $12.00  
  Purchase #5 $215.38   10.628%   $238.2706   $238.27   $238.25   $238.30  
  Purchase #6 $220.95   10.767%   $244.7397   $244.74   $244.75   $244.70  
  Purchase #7 $92.43   6.760%   $98.6783   $98.68   $98.70   $98.70  
  7 purchase totals = $954.87       $1,035.6649   $1,035.67   $1,035.65   $1,035.60