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 $208.76   5.348%   $219.9245   $219.92   $219.90   $219.90  
  Purchase #2 $116.91   8.347%   $126.6685   $126.67   $126.65   $126.70  
  Purchase #3 $232.51   7.567%   $250.104   $250.10   $250.10   $250.10  
  Purchase #4 $37.38   3.795%   $38.7986   $38.80   $38.80   $38.80  
  Purchase #5 $150.86   11.359%   $167.9962   $168.00   $168.00   $168.00  
  Purchase #6 $6.84   9.286%   $7.4752   $7.48   $7.50   $7.50  
  Purchase #7 $59.80   4.489%   $62.4844   $62.48   $62.50   $62.50  
  7 purchase totals = $813.06       $873.4514   $873.45   $873.45   $873.50