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 $58.94   4.504%   $61.5947   $61.59   $61.60   $61.60  
  Purchase #2 $207.30   12.756%   $233.7432   $233.74   $233.75   $233.70  
  Purchase #3 $240.35   11.473%   $267.9254   $267.93   $267.95   $267.90  
  Purchase #4 $207.74   5.540%   $219.2488   $219.25   $219.25   $219.20  
  Purchase #5 $209.72   7.785%   $226.0467   $226.05   $226.05   $226.00  
  Purchase #6 $141.76   11.654%   $158.2807   $158.28   $158.30   $158.30  
  Purchase #7 $95.54   12.175%   $107.172   $107.17   $107.15   $107.20  
  7 purchase totals = $1,161.35       $1,274.0115   $1,274.01   $1,274.05   $1,273.90