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 $241.97   9.264%   $264.3861   $264.39   $264.40   $264.40  
  Purchase #2 $100.68   4.482%   $105.1925   $105.19   $105.20   $105.20  
  Purchase #3 $71.88   4.576%   $75.1692   $75.17   $75.15   $75.20  
  Purchase #4 $235.83   3.479%   $244.0345   $244.03   $244.05   $244.00  
  Purchase #5 $73.49   11.536%   $81.9678   $81.97   $81.95   $82.00  
  Purchase #6 $111.67   6.457%   $118.8805   $118.88   $118.90   $118.90  
  Purchase #7 $120.76   3.650%   $125.1677   $125.17   $125.15   $125.20  
  7 purchase totals = $956.28       $1,014.7983   $1,014.80   $1,014.80   $1,014.90