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 $192.63   11.588%   $214.952   $214.95   $214.95   $215.00  
  Purchase #2 $29.74   4.591%   $31.1054   $31.11   $31.10   $31.10  
  Purchase #3 $158.76   11.744%   $177.4048   $177.40   $177.40   $177.40  
  Purchase #4 $228.58   6.526%   $243.4971   $243.50   $243.50   $243.50  
  Purchase #5 $162.82   13.279%   $184.4409   $184.44   $184.45   $184.40  
  Purchase #6 $37.99   12.127%   $42.597   $42.60   $42.60   $42.60  
  Purchase #7 $61.92   10.656%   $68.5182   $68.52   $68.50   $68.50  
  7 purchase totals = $872.44       $962.5154   $962.52   $962.50   $962.50