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 $194.99   10.261%   $214.9979   $215.00   $215.00   $215.00  
  Purchase #2 $165.46   11.665%   $184.7609   $184.76   $184.75   $184.80  
  Purchase #3 $217.70   6.675%   $232.2315   $232.23   $232.25   $232.20  
  Purchase #4 $57.72   6.643%   $61.5543   $61.55   $61.55   $61.60  
  Purchase #5 $122.36   6.696%   $130.5532   $130.55   $130.55   $130.60  
  Purchase #6 $188.89   3.555%   $195.605   $195.61   $195.60   $195.60  
  Purchase #7 $25.79   12.470%   $29.006   $29.01   $29.00   $29.00  
  7 purchase totals = $972.91       $1,048.7088   $1,048.71   $1,048.70   $1,048.80