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 $243.64   7.554%   $262.0446   $262.04   $262.05   $262.00  
  Purchase #2 $213.51   8.402%   $231.4491   $231.45   $231.45   $231.40  
  Purchase #3 $57.37   4.828%   $60.1398   $60.14   $60.15   $60.10  
  Purchase #4 $220.86   3.676%   $228.9788   $228.98   $229.00   $229.00  
  Purchase #5 $194.57   9.781%   $213.6009   $213.60   $213.60   $213.60  
  Purchase #6 $128.97   5.591%   $136.1807   $136.18   $136.20   $136.20  
  Purchase #7 $39.28   9.624%   $43.0603   $43.06   $43.05   $43.10  
  7 purchase totals = $1,098.20       $1,175.4542   $1,175.45   $1,175.50   $1,175.40