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 $231.28   13.714%   $262.9977   $263.00   $263.00   $263.00  
  Purchase #2 $31.92   3.416%   $33.0104   $33.01   $33.00   $33.00  
  Purchase #3 $246.88   12.209%   $277.0216   $277.02   $277.00   $277.00  
  Purchase #4 $121.73   3.597%   $126.1086   $126.11   $126.10   $126.10  
  Purchase #5 $149.27   4.289%   $155.6722   $155.67   $155.65   $155.70  
  Purchase #6 $53.31   11.266%   $59.3159   $59.32   $59.30   $59.30  
  Purchase #7 $124.76   6.440%   $132.7945   $132.79   $132.80   $132.80  
  7 purchase totals = $959.15       $1,046.9209   $1,046.92   $1,046.85   $1,046.90