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 $46.86   6.513%   $49.912   $49.91   $49.90   $49.90  
  Purchase #2 $119.65   11.370%   $133.2542   $133.25   $133.25   $133.30  
  Purchase #3 $154.51   9.479%   $169.156   $169.16   $169.15   $169.20  
  Purchase #4 $87.50   3.533%   $90.5914   $90.59   $90.60   $90.60  
  Purchase #5 $183.38   11.655%   $204.7529   $204.75   $204.75   $204.80  
  Purchase #6 $12.87   12.350%   $14.4594   $14.46   $14.45   $14.50  
  Purchase #7 $128.87   4.349%   $134.4746   $134.47   $134.45   $134.50  
  7 purchase totals = $733.64       $796.6005   $796.59   $796.55   $796.80