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 $182.41   8.313%   $197.5737   $197.57   $197.55   $197.60  
  Purchase #2 $193.65   6.385%   $206.0146   $206.01   $206.00   $206.00  
  Purchase #3 $53.44   9.543%   $58.5398   $58.54   $58.55   $58.50  
  Purchase #4 $243.37   8.326%   $263.633   $263.63   $263.65   $263.60  
  Purchase #5 $8.49   7.871%   $9.1582   $9.16   $9.15   $9.20  
  Purchase #6 $63.94   6.814%   $68.2969   $68.30   $68.30   $68.30  
  Purchase #7 $247.46   10.495%   $273.4309   $273.43   $273.45   $273.40  
  7 purchase totals = $992.76       $1,076.6471   $1,076.64   $1,076.65   $1,076.60