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 $60.53   3.656%   $62.743   $62.74   $62.75   $62.70  
  Purchase #2 $103.95   7.526%   $111.7733   $111.77   $111.75   $111.80  
  Purchase #3 $75.81   11.576%   $84.5858   $84.59   $84.60   $84.60  
  Purchase #4 $7.44   13.292%   $8.4289   $8.43   $8.45   $8.40  
  Purchase #5 $77.84   12.418%   $87.5062   $87.51   $87.50   $87.50  
  Purchase #6 $202.87   3.843%   $210.6663   $210.67   $210.65   $210.70  
  Purchase #7 $47.91   12.561%   $53.928   $53.93   $53.95   $53.90  
  7 purchase totals = $576.35       $619.6315   $619.64   $619.65   $619.60