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 $60.31   3.737%   $62.5638   $62.56   $62.55   $62.60  
  Purchase #2 $103.98   7.252%   $111.5206   $111.52   $111.50   $111.50  
  Purchase #3 $202.60   13.558%   $230.0685   $230.07   $230.05   $230.10  
  Purchase #4 $203.92   8.788%   $221.8405   $221.84   $221.85   $221.80  
  Purchase #5 $200.62   8.388%   $217.448   $217.45   $217.45   $217.40  
  Purchase #6 $178.49   4.537%   $186.5881   $186.59   $186.60   $186.60  
  Purchase #7 $20.89   10.512%   $23.086   $23.09   $23.10   $23.10  
  7 purchase totals = $970.81       $1,053.1155   $1,053.12   $1,053.10   $1,053.10