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 $212.59   6.675%   $226.7804   $226.78   $226.80   $226.80  
  Purchase #2 $235.54   3.834%   $244.5706   $244.57   $244.55   $244.60  
  Purchase #3 $38.90   12.453%   $43.7442   $43.74   $43.75   $43.70  
  Purchase #4 $84.57   3.341%   $87.3955   $87.40   $87.40   $87.40  
  Purchase #5 $243.73   7.590%   $262.2291   $262.23   $262.25   $262.20  
  Purchase #6 $182.99   10.656%   $202.4894   $202.49   $202.50   $202.50  
  Purchase #7 $129.85   3.251%   $134.0714   $134.07   $134.05   $134.10  
  7 purchase totals = $1,128.17       $1,201.2806   $1,201.28   $1,201.30   $1,201.30