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 $232.25   9.358%   $253.984   $253.98   $254.00   $254.00  
  Purchase #2 $80.49   7.707%   $86.6934   $86.69   $86.70   $86.70  
  Purchase #3 $118.93   4.404%   $124.1677   $124.17   $124.15   $124.20  
  Purchase #4 $97.90   3.132%   $100.9662   $100.97   $100.95   $101.00  
  Purchase #5 $29.91   12.203%   $33.5599   $33.56   $33.55   $33.60  
  Purchase #6 $237.56   3.743%   $246.4519   $246.45   $246.45   $246.50  
  Purchase #7 $71.91   12.135%   $80.6363   $80.64   $80.65   $80.60  
  7 purchase totals = $868.95       $926.4594   $926.46   $926.45   $926.60