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 $54.78   11.461%   $61.0583   $61.06   $61.05   $61.10  
  Purchase #2 $227.42   11.178%   $252.841   $252.84   $252.85   $252.80  
  Purchase #3 $184.26   5.338%   $194.0958   $194.10   $194.10   $194.10  
  Purchase #4 $77.62   3.859%   $80.6154   $80.62   $80.60   $80.60  
  Purchase #5 $163.99   13.555%   $186.2188   $186.22   $186.20   $186.20  
  Purchase #6 $18.76   6.697%   $20.0164   $20.02   $20.00   $20.00  
  Purchase #7 $243.44   9.616%   $266.8492   $266.85   $266.85   $266.80  
  7 purchase totals = $970.27       $1,061.6949   $1,061.71   $1,061.65   $1,061.60