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 $161.33   13.292%   $182.774   $182.77   $182.75   $182.80  
  Purchase #2 $135.66   10.814%   $150.3303   $150.33   $150.35   $150.30  
  Purchase #3 $135.58   7.807%   $146.1647   $146.16   $146.15   $146.20  
  Purchase #4 $33.79   5.344%   $35.5957   $35.60   $35.60   $35.60  
  Purchase #5 $6.56   7.591%   $7.058   $7.06   $7.05   $7.10  
  Purchase #6 $225.39   11.849%   $252.0965   $252.10   $252.10   $252.10  
  Purchase #7 $225.39   10.367%   $248.7562   $248.76   $248.75   $248.80  
  7 purchase totals = $923.70       $1,022.7754   $1,022.78   $1,022.75   $1,022.90